as quickly as possible, especially the younger parts, taking as much trouble over it as over the larvæ. They also cover it up again as soon as possible to protect it from the light. A nest, I metre x 50 cm. was opened, and in twenty-four hours the ants had put on a new roof 10 cm. deep. They also carry the nest with them upon their migrations

5. The Use of the Garden: its Construction and its Tendance observed in Captivity.-Some ants' nests were placed under a bell jar and supplied with leaves; they inade no use of them and presently died. If they were supplied with a piece of "garden," they rebuilt it and covered it so far as they could. It was seen to shrink from day to day, the ants bringing out the old pieces and adding them to the wall; finally it was exhausted and the ants died. Others were starved for five days, and then supplied with a bit of garden; they at once began to eat the Kohl-rabi clumps. It was found by this means that each species of Atta will eat the Kohl-rabi of the other three as well as its own. Finally, by supplying the ants with bits of garden, a damp sandy floor, and fresh leaves, they were induced to build in captivity. The dish in which they worked was covered by a glass lid, and when this was covered with a dark cloth or otherwise kept dark, the ants built under it without covering the garden. In this way the whole process was observed An ant bringing in a piece of leaf proceeds to cut it into halves, repeating the process till it has got a very small piece left, which it holds between its fore feet and turns round, crushing it in its jaws until the whole is reduced to a round ball of pulp about 25 mm. thick. This it then takes and adds to the garden. So well is the kneading performed that no single cell remains uninjured, and it was observed that the hyphæ of the fungus grew through and round one of these particles within a few hours. Belt supposed that this process was performed by the small workers abovementioned, but it is not so, as we have just seen. The small workers perform the function of weeding the garden, and this is so well done that a portion of it removed and grown in a nutrient solution gives a perfectly pure culture, not even containing bacteria !

6. Development of the Fungus after removal of the ants; the conidia," pearl-hypha," and strand-swellings. Result of the artificial culture of the Fungus.-If a portion of garden be left to itself in darkness, the ants having been removed, aerial-hyphae develop in a thick mass several centimetres high, with many anastomoses; the Kohl-rabi clumps are used up in the process, apparently supplying material for it. The formation of conidia now takes place all over the mass. From a hypha there buds out a lateral projection, which bears branches arranged roughly in whorls upon these are again borne whorls of small clubshaped branches, from whose ends are abstricted rows of conidia, whose diameter is 2; there are, as a rule, not more than ten in a row. Occasionally the formation of the strings of conidia occurs not only on the final branches, but also on those of the preceding order. After the conidia are formed the mass collapses (about the fifth day).

About the third day a careful search reveals among the ordinary hyphæ a few which are covered, as with rows of pearls, with small spherical lateral protuberances. These "pearl-hypha" arise from the ordinary ones. The cavity of the "pearl" is in direct communication with that of the hypha itself, and contains protoplasm. In connection with these there occurs a second type of conidia formation, distinguished by Möller as the "weak" formation. There is no preliminary branching, the conidia being abstricted from the ends of the pearl hypha, or plain hyphae in connection with them. The end of the hypha swells up and bears the conidiophores. The chains generally consist of at least twenty conidia. Still a third form of hypha is to be found. Sooner or later there are observed on the garden thick white strands,

which on examination are found to consist of hyphæ, which look like rows of beads, or yeast-chains, and are much bent, branched, and twisted. From these there arise pearl hyphæ, or we may find pearls upon these hyphæ themselves. These peculiar hyphæ arise first of all as "pearls" on ordinary hypha, and then a process of budding goes on, just like that which gives rise to yeast chains. The "pearls" might be looked upon as homologous with these lateral swellings of hyphæ, but there is also another view, that they represent rudimentary conidiophores. It has been seen above that the conidiophores in the "strong" conidia formation are not always confined to the ends of the hyphæ, but may at times appear further back, and it is suggested that originally they were borne anywhere upon the hypha, and subsequently restricted to the tips, the "pearls" then representing rudimentary conidiophores. The "pearl" hyphæ and weak conidia formation are usually found in connection with these swollen strands, and on one or two occasions a connection was found with the strong conidia formation.

When a few ants were left with a large piece of garden, they did their utmost to prevent the formation of these aerial hyphæ, &c., biting them off as they appeared, but gradually the fungus gained the upper hand of them. Proceeding now to the results of culture in nutrient solutions, the strong conidia germinate and give rise to hypha which ultimately bear strong conidia again. Never did the "weak" form appear, but very often from the main hypha there were given off lateral branches, some of which developed into rows of beads, like the hyphæ described above, and others swelled up at the ends just like the Kohl-rabi. The cultures being pure, these formations could not be pathological, produced by bacteria, as is sometimes the case.

Similarly the weak conidia gave rise only to conidia like themselves. Pearl-hyphae were occasionally formed, and rarely the peculiar hyphæ like rows of beads.

When one of these forms was grown in one culture drop, and bent over into another drop, in which the other form was, the two anastomosed freely, showing that they belonged to the same plant.

When a portion of Kohl-rabi is grown in the solution it gives rise to ordinary hypha, which ultimately produce a new crop of Kohl-rabi. On one occasion it gave rise to pearl-hyphæ and weak conidia.

To sum up, the fungus has two conidia forms, which develop upon the garden in the absence of the ants. The mycelium shows a strongly marked tendency to the formation of swellings and protuberances, which appear in a different form, more or less distinctly marked. One of these, which has probably reached its present form under the cultivation and selection of the ants, is the Kohl-rabi.

7. Discovery of the Highest Fructification of the Fungus.-It being evident that the fungus was either a Basidiomycete or Ascomycete, attempts were made to obtain its principal fructification by cultivation, but in vain. A fortunate discovery, however, was made of a nest which had a huge red Amanita-like fungus growing out of it. This was found to belong to the genus Rozites, and the species was named R. gongylophora. The development of the basidia, &c., is given in detail, but need not be gone into here. Cultivation of the spores showed that this was indeed the fructification of the Kohl-rabiforming fungus.

10. Plants attacked by Leaf-cutting Ants.-These were found to be very numerous, and no rule could be formulated as to the operations of the ants. On one day they would strip one plant and the next day leave it untouched, or vice versa. An interesting case was observed in the cold weather. An army of leaf-cutters was found stripping a Cecropia, though the latter was inhabited at the time by its protecting ants! The latter appeared to be too numbed by the cold to go out and fight.

THE GARDENS OF THE HAIRY ANTS. While working at the preceding it was discovered that somewhat similar fungus gardens cccur in the nests of Apterostigma. Four species were studied. All have the same fungus, belonging apparently, however, to a different genus from Rozites. These hairy ants live in decaying wood and have small gardens 4-8 cm. in diameter, built of bits of wood-fibre, beetle-dung, &c. The chief point of interest is that though all have the same fungus yet all have not cultivated and selected the Kohlrabi to the same degree. A. Wasmanni, Forel, has a well-developed type with large spherical swellings on the ends of the hypha. The others have Kohl-rabi of a much lower type, the hyphæ being only slightly swollen into a club shape, and they are not aggregated into regular groups.

It was, as usual, found impossible to obtain by artificial culture the highest fructification of the fungus, so its systematic position is still undetermined.

THE GARDENS OF CYPHOMYRMEX.

This genus of ants is closely related to the two preceding, and the two species examined (C. auritus, Mayr, and C. strigatus, Mayr) are also fungus-growers. Both form nests like those of Apterostigma, and use similar material in the garden. The two species have the same fungus, but C. strigatus obtains far finer Kohl-rabi than C. auritus, just as we have seen to be the case with the species of Apterostigma. It is thus pretty evident that the large size of the best Kohl-rabi must be due to selection and cultivation on the part of the ants.

The concluding pages of the work are taken up by a discussion of the mycological results of these investiga tions, for which reference must be made to the original. The work is illustrated by beautiful plates, and forms as a whole one of the most fascinating contributions to botanical literature that have been made for many years. JOHN C. WILLIS.

A FEW REMARKS ON INSECT PREVALENCE DURING THE SUMMER OF 1893.

WE are hearing a great deal just now of unusual

amount of insect presence, and there appears no reason to doubt that such is very much the case, although for scientific use we need much more of reliable report than we possess as to what kinds of insects are noticeably more present than in seasons of ordinary meteorological conditions, and also we need observations as to what kinds may be unusually absent.

So far as my own acquaintance with the subject (which is mainly in reference to amount of presence of crop insects) allows me to judge, these unusually large amounts where they occur-for the superabundance does not affect all kinds-may be attributed to weather influence acting either directly on the development of the insects themselves, or so affecting the state of their crop-food-plants as to induce the conditions which we know well by the agricultural experience of many years are favourable to establishment of infestation.

The important preliminary as to there having been really such a definite deficiency in rainfall as to amount to what may be called "a drought" over England and Wales, we have stated shortly in the Monthly Meteoro logical Magazine, of Mr. G. J. Symons, F.R.S., No. cccxxxi, p. 98, as follows :-" Assuming that the twentyfour stations fairly represent England and Wales, we find that in March the rainfall was only one-third of the average, in April one-sixth, in May three-quarters, and in June two-thirds." Mr. Symons further points out that "this, of course, is taking the country as a whole; at many individual stations the results would be much more striking, e.g. at Bodmin in the three months" (March to May) "only one fifth of the average fell."

Amongst insect attacks especially subject to increase

by stunting of growth, or over-maturation of sap of their food plants, are those of the Aphides or Plant Lice. which have been- so far as my own contributors' report. show-unusually early and prevalent this year. They were forwarded on mangolds from Devonshire almost 1 soon as there could be said to be good accommodation for attack on the leafage, and turnips and cabbage leafage. damson early in the season, and larch later on the borders of England and Scotland, were some of the tree and food plant habitats which were exceptionally afflicted These prevalences agree with the rule of Aphis life and down by Mr. G. B. Buckton, F.R.S., our great authorit on Aphis life. In drawing attention to the abnormally rapid increase of Aphides under some circumstances, he accounts for it by maturity (e. power of reproduction taking place earlier in the life stage where from various causes inducing want of supply of nutriment, structural changes occur consequently on these in the larvae of the Aphides subsequently born. (See "Brit. Aphides,' b G. B. Buckton, F.R S., vol. i. p. 72).

Besides the above reasons for increase, we have also the negative reason of absence of destruction by goou drenching rains to wash off and often to drown the enemy. One of my correspondents wrote me that he ha been doing this or that, but the best help was the we come rain.

The above may be taken as a type of one way in which weather influence acts; in the case of wasps, which popt larly represent much of insect presence to the world at large, we have another set of influences.

Our recent drought began in March. In many years we have the most variable weather at this season and the queen wasps, the foundresses of the comin colonies, being tempted from their winter localities of hybernation by a day or two's warmth, are caught, it may be, by heavy rain, or by snow, or by frost, and perish This year weather was more favourable to them, and we had not the drenching rains which in an ordinary year put an end to many an embryo nest with its few grubs whether in ground or hedge. The first commenceinen", formed of a tiny piece of paper, in shape like an un brella, with beneath it a pendant ending in a club formed of a few cells, each with its egg or young maggot tenant, is delicate in the extreme. If the cavity in which it is placed in the ground is flooded, its destruction is certain, or if in storms the foundress cannot return to feed the young family they must perish.

In the case of wasps, probably weather influences. which affect amount of any particular kind of food are as. little troublesome as to any insect. All who at all stod their habits are aware that flesh, fish, insects to a large amount, and fruit to utter rapacity of consumption, are constantly utilised by them for their own special support or that of the maggot family. To what extent the ace : wasps may feed on other than vegetable matter I cannot say, but dissection and examination of the undigested food in the blind pouch of the food canal of the larva! wasp has shown this to consist of remains both of anim. and vegetable matter; in the record before me chiefly of insect débris. Their varied kind of food and their wonderful adaptability of instinct in making adverse cutcumstances suitable for the household needs, make the wasp family when once established, most prolific pests.

The great prevalence of what are called surface caterpillars, that is, the larvæ of various kinds of Agrotis at the roots of various kinds of field crops, gives an example of increase of presence of the Lepidoptera, under circumstances favourable to the development of the imago from the chrysalis, and subsequently to the pairing of the moths and successful egg deposit. In wet and chill weather, when the moths hang about torpidly, a certain proportion of them get drenched, so that their wings are of little service; the larva are injured in different ways, or disease induced, much influencing amount of presence.

In the past season such attacks as that of the great caterpillars (four inches or more in length) of the Lappet Moth, the Gastropacha quercifolia scientifically, to apple leafage; or again, the presence of caterpillars of the little Pyralis glaucinalis might reasonably be supposed to be influenced by weather. In the first case, the great size of the larva feeding on the leafy twig exposes it much to alternations of weather, and in the second, where, as in the samples sent me, the infestation was located in the outer part of fodder stacks, the penetration of wet which might soak the filmy cocoons with their developing contents, would cause conditions very different to the longcontinued appearances of the present summer.

To go through the different orders of insects, specially represented, or the different dates and amounts of their appearance on the crops, would be too long here, but I can safely say that whilst the drought lasted I had constant applications regarding insect appearances, including a much greater variety than usual of kinds little observed in ordinary years, and in some cases unusual amount of presence of our common kinds.

Various representatives of the Acarina, as the currant, pear, and plum Phytopti were of course largely noticed, as also the Phytopti (or gall mites) of the hazel buds, of which the galls loaded the hazel boughs in this neighbourhood early in May to a degree I have never before seen. The kind of (so-called) "red spider" Bryobia pratiosa) which ordinarily is chiefly found on Ivy, extended its injurious presence so widely to gooseberry leafage as to necessitate careful, and happily successful, measures to get it under.

Why, with all this, various crop insect attacks were less reported than customarily remains uncertain. Corn Aphides as yet have not been complained of. Possibly this is by reason of the heat hardening the ears so that they were in a condition to withstand attack before the Aphides arrived on the heads to endeavour to pierce into them with their suckers. In countries where the climatal conditions can be counted on, this point (of arranging date of crop so as to protect itself from attack) is one of the regular methods of prevention. Another infestation which threatened to be very troublesome, but of which the second brood did not make any noteworthy appearance in various places, is that of the mustard beetle. Why this should be so I am as entirely at a loss to explain as the crop inspector who reported the state of things to me.

Various other absences of attack remain also unexplained, but are duly noted for possible future service in agricultural entomology.

So far as I can gather from contribution of my own. correspondents, or other accessible sources of information, I should consider that such extra amount of insect presence as has occurred, has been owing to weather influence. We have had earlier and more numerous development of many kinds, and also in the case of various common crop insect pests, the hardness of the soil, and other conditions incident to drought, which made it totally impossible to bring either stimulating dressings, or mechanical measures to bear, necessitated our permitting increase to go on unchecked in some cases, and in some, though the caterpillars just below the surface of the ground necessarily did not themselves multiply, their unattainable legions swelled the numbers of observable pests, and probably will supply us a plentiful brood of moths for further continuation of species.

There does not appear to be any reason from previous circumstances, or from importations, to consider that we were suffering from other than the ordinary attacks, which, in a changeable climate like ours, must be changeable in their amounts; at least, so it appears to me from such an amount of report as I possess. ELEANOR A. ORMEROD.

Mr.

At Greenwich the temperature exceeded 80° on each successive day from the 8th to the 18th inclusive, the highest readings being 93° on the 16th, 94°2 on the 17th, and 951 on the 18th. The last reading has only been exceeded twice at any time of the year during the last half-century, viz., 96 6 on July 22, 1868, and 97 1 on July 15, 1881. The highest reading in the sun during the eleven days in question was 146 2 on the 18th, but this temperature was slightly exceeded in June last. Symons states that, on the 18th instant, the thermometer at his station at Camden Town registered 93 6, which has only once been exceeded during thirty-six years (1858-93), viz., on July 15, 1881, when it read one degree higher; the present is the only year with a maximum shade temperature above 90 for three consecutive days. On the night of the 17th instant the minimum temperature in South London was as high as 72, being rather above the average maximum temperature for the month of August, and the daily mean, as deduced from the maximum and minimum readings in the Daily Weather Report for the 18th, was 825; this mean value is probably the highest on record since trustworthy observations have been taken. In a valuable paper recently read by Mr. Ellis before the Royal Meteorological Society, the average mean temperature at Greenwich for that day is given as 62 5.

On the Continent the highest readings quoted in the Faily Weather Report were 102 and 106 at Rochefort in France on the 13th and 14th instant, while the maximum readings there reached or exceeded go on seven consecutive days. In the South of France the temperature exceeded So on each day of the period in question, 100 being recorded at Biarritz on the 17th.

The Weather Charts published by the Meteorological

Office during this period show that the conditions were mostly anti-cyclonic, both over this country and the Continent, with the exception of a depression in the south-west, which caused some sharp thunderstorms on the 9th and 10th. On the 18th another depression appeared off our north-west coasts, causing a gale in those parts, while strong winds and lightning occurred generally, with heavy rain in the west. These conditions checked the excessive heat; on the 19th the maximum temperature in London was 15, and at Paris 25°, lower than on the previous day.

TH

A SENSItive sphEROMETER.

HE ordinary spherometer has three arms carrying three fixed points, with a point moved by a screw in the centre. This form is an improvement on the original spherometer invented by Andrew Ross, and for which the Society of Arts gave him a silver medal in 1841.

A description of Ross's instrument is given by Holtzapffel, vol. iii. p. 1271 of his work on "Turning and Mechanical Manipulation," extracted from vol. liii. of the Transactions of the Society of Arts. This instrument could measure to Too of an inch, and by estimation half this amount. An ordinary spherometer, with a screw of of an inch pitch and head divided to hundredths, will measure to 10000 of an inch.

I pointed out in vol. 1. page 145, of the Memoirs of the Royal Astronomical Society that the sensitiveness of the ordinary spherometer was much increased by placing the screw not in the centre, but in one of the arms in place of one of the fixed points; this at once increased the sensitiveness of the screw in proportion to the distance of the screw from the nearest fixed point, and this fixed point from a line joining the other two fixed points. The improvement I wish to bring before those interested in spherometers by this note, is the extension of this principle, for by carrying the middle point much nearer the line joining the other two, a proportionate increase of sensitiveness is obtained.

In the case of an instrument I have made on this plan I have increased the sensitiveness thirty times, the distance from the middle point to the screw being three inches, and the distance of the point from the line of the other two being of an inch; with a screw of one hundred threads to the inch and a head divided to hundredths, the ordinary form of instrument will read to 10000, but on the plan I give, the same screw will measure 300000 of an inch.

There is an additional advantage in this form, that the curvature of a part nearly in a line is measured, so that cross measures can be taken.

The form of the instrument is not symmetrical, and it requires to be balanced, so that when the screw is raised it will be possible to estimate the frictional contact of the outside points when the middle one is taking the weight. This balancing is easily done by adding a handle to the part opposite the arm carrying the screw; in practice it is found that this handle is of the greatest value in keeping the heat of the hand from the instrument, as even with the ordinary instrument, holding it for a short time in the hand alters the readings materially.

It is of great advantage to have on the arms carrying the two outer pins two pieces of wood or ivory projecting not quite as much as the measuring points, so that by tilting the instrument up these two pieces come first into contact with the surface to be measured, then by gradually raising the handle the points are brought gently into contact. The figure is a plan of this spherometer, and shows the position of the three fixed points PPP with reference to the measuring screw S, and the position of the balancing handle H with reference to the un

P

PLAN

for which, indeed, it was designed. To make it available for measuring differences between parts of a curved surface of considerable curvature the middle pin should be a screw capable of movement to, and clamping, in a position, that will allow the measuring screw to work.

DAN

A. A. COMMON.

JEAN DANIEL COLLADON.

ANIEL COLLADON, the celebrated physicist and engineer, died on June 30, at Cologny, near Geneva. Colladon was born at Geneva, December 15, 1802. He belonged to a Protestant family from Berry, which removed from France, in the middle of the sixteenth century, on account of religious persecutions, and found refuge in Calvin's town. Many a distinguished magistrate came from this family, amongst others the learned juris-consult, Germain Colladon.

While still quite young Colladon proved to be wonderfully intelligent, and had a remarkably observant mind.

He went through the College and then the Academy of Geneva, which at that time had, among its professors. A. P. de Candolle, M. Aug. Pictet, Th.de Saussure and Prevost. His liking for science could not but develop itself in contact with these eminent men, whose esteem he soon gained.

At the age of ten years he made friends with Charles Sturm, who became a noted mathematician, and was on later occasions his fellow-worker. His inventive nature and talent for experimental inquiry turned itself above all to physics and its mechanical applications.

He was just twenty-two when he received from the Society of Science of Lille a first prize for the invention of a new photometer. At twenty-three he went to finish his studies at Paris. He lived there for about ten years, leading a simple life, almost entirely devoted to work.

He was received in a most flattering manner for such a young man by the pleiades of celebrated men, which the