on the lookout for all sorts of changes in colour, food, nesting habits, colours of eggs, and so on; trout grew so rapidly in the streams and lakes into which they were introduced as to belie all previously recorded experience. The same thing occurred among plants. Watercress-a plant of two to four feet in length in European waters-grew in some streams to a length of from twelve to fourteen feet, and with stems as thick as one's wrist; the common spear-thistle, which is from two to five feet high in Britain, formed in some districts vast impenetrable thickets six to seven feet in height; brambles, briars and other weeds took possession of whole districts, and threatened to choke out all other vegetation. It seemed indeed as if the laws of natural selection and the principle of the survival of the fittest had been temporarily suspended, and nature was running riot.

It is no wonder that all the younger naturalists in the country were almost inclined to think that perhaps we would here see the rise of new varieties, which would become "fixed," and would soon rank as "species," distinct from those from which they were descended. It may be that our ideas as to what constituted varietal and specific distinction were somewhat vague-in that respect we were not very different from the majority of those who used these terms in a somewhat loose manner-but there they were. Some such feeling was still in my mind as late as 1891, when I read a short paper before the Biological Section of the Australasian Association for the Advancement of Science at its Christchurch meeting, "On Some Aspects of Acclimatisation in New Zealand." The following sentences show the trend of my views at the time:

One of the most interesting points connected with the successful naturalisation of foreign species is the observation of the changes which they undergo in their altered conditions. Nearly all our introduced animals have been brought from lands where the struggle for existence is very keen, and where natural enemies abound. In their new home they have been set free from these old trammels, and the enemies have been left behind. Under such circumstances it is not surprising to find that sports in colour, which in Europe would be strictly eliminated as soon as they appeared, owing to their rendering their possessors too conspicuous to their enemies, are here preserved and tend to be reproduced.

I then went on to instance what occurs among hares, rabbits, sparrows and other birds, humble-bees, etc., both with regard to change of colour and of habits. My mind was evidently quite prepared to find such changes, though I had to admit that the evidence sought for was not forthcoming to any extent.

The subject continued to occupy my thoughts from time to time, but I was not able to devote much consecutive attention to it until 1915, when it seemed advisable to me to resume the thread of my

ideas as propounded twenty years previously, and see how far these views were correct. It soon, however, became apparent to me that it would be a much more important work, and one preliminary to any exhaustive examination of the subject, to ascertain-as far as possible-what species of animals and plants had become naturalised in the country; what species had failed to establish themselves; to seek for the reasons of their success or failure; and to ascertain what effects had been produced on the native fauna and flora.

Changes in Indigenous Fauna due to Naturalisation of Foreign Species

The question is sometimes asked: "What effects have been produced on the native fauna by the introduction of foreign animals and plants into the islands of the New Zealand group?" Any answer which can be given can only at best suggest some of the changes which have taken place. The effects have been so far-reaching and so complex that it is impossible to present any summary of them, and all that can be done is to show various aspects of the problem, and to consider facts in detail.

When knowledge of the native fauna first began to be acquired considerable changes had already commenced to take place, and others were in progress. It was, however, long before any systematic knowledge of the indigenous animals was accumulated and published, and it must be borne in mind that as far as the terrestrial invertebrates are concerned, this knowledge is still very fragmentary. Indeed for many groups, as for example, that of the Insects, it is probably the case that the fullest catalogue which could be made to-day would not include many species which were in existence at the time of Cook's first visit to these islands. Probably very many species have either ceased to exist, or have become very rare. There is no actual knowledge of the fact, it is only inferred from what we know to have taken place with regard to native birds and lizards. But that profound changes have taken place is familiar to all who have observed the development of the last fifty years. The changes have, necessarily, been most rapid during the latter half of last century and since, and especially from the time that the various acclimatisation societies sprang into activity.

An examination of the published papers and books on the zoology of New Zealand shows that very much of the present knowledge of the subject is quite recent. Since the days of Captain Cook isolated papers on the zoology appeared in many and various publications, especially during last century, and a good deal of general information was accumulated. A good summary of this is to be found in Hutton's Introduction to the Index Fauna Nova Zealandia. Apparently the

first full lists, as far as they go, are contained in the appendix to Dieffenbach's Travels, published in 1843. In this work, J. E. Gray gives a catalogue of 84 species of birds and six species of lizards.

In 1862 Gray in The Ibis gave a synopsis of the birds collected in the "Voyage of M.M.S.S. Erebus and Terror," and enumerated 122 species as occurring in New Zealand and the Chatham Islands. Buller's Birds of New Zealand, published in 1873, contained descriptions of 147 species; his Manual in 1882, gave 176 species; and the second edition of the Birds of New Zealand in 1888, recorded 195 species. The Index Fauna Nova Zealandia (1904) gives 194 species of permanent birds, 222 of wandering species, and 15 species of lizards.

Fishes are first recorded in 1843 in Richardson's list (Dieffenbach), where 92 species are named. In Hector and Hutton's Catalogue in 1872, 141 species are recorded; the Index (1903) gives 254 names. Yet the fishes are very imperfectly known even yet.

J. E. Gray in 1843 gives a list of 222 species of Mollusca and 3 species of Brachiopoda; Hutton's Manual of Mollusca, published in 1880, gives 598 species of Mollusca, 8 of Brachiopoda, and 191 of Polyzoa; while Suter's Manual in 1913 gives 1187 species of Mollusca.

list

White and Doubleday wrote the account of Insecta for Dieffenbach's work in 1843, and referred to the following numbers of insects, namely: Orthoptera, 4 species; Hymenoptera, 5; Coleoptera, 50; Lepidoptera, 23; Diptera, 6; Neuroptera, 2; Homoptera, 4; and Hemiptera, 3; a total of 97 species. In 1873 Hutton published of New Zealand insects of the above eight orders containing 742 species, of which 265 were Coleoptera. Captain Broun brought out his first Manual of Coleoptera in 1880, and it contained 1321 species. In 1881 Hutton's Catalogue of Diptera, Orthoptera and Hymenoptera brought up the number of species in these three orders from 151 (1873) to 227. In 1898 Hudson's Moths and Butterflies described 238 species of Macro-lepidoptera alone. Finally, the following numbers are given in the Index Fauna Nova Zealandia (1903): Hymenoptera, 155; Lepidoptera, 608; Diptera, 343; Coleoptera, 2787; Hemiptera, 166; Neuroptera, 60; Orthoptera, 17; and Aptera, 3; making a total of 4139 species, a number which has been considerably added to since. Many of these orders of insects are still very imperfectly known.

White and Doubleday in 1843 recorded 11 spiders and 2 Myriapods; the Index (1903) gives 251 species of Arachnida and 30 of Myriapods. Similarly the same authors name 30 species of Crustacea; Miers' Catalogue of Stalk- and Sessile-eyed Crustacea (1876) describes 140 species; while the Index records 532 species-a number which has since been increased to over 600 species.

I quote this rather formidable list of figures to show how greatly our systematic knowledge of the fauna has been extended within the last seventy years.

Mr Hedley suggests that as the European or cosmopolitan weedflorula is able, with human assistance, to oust the indigenous flora, so there may be a weed-faunula (mouse, sparrow, snail, etc.) which may act similarly on the indigenous fauna.

At the date of my arrival in the country (1868) the following nine species of birds, which have either altogether or to a great extent disappeared since, were to be met with, in some cases fairly commonly: native crows (Glaucopis wilsoni and G. cinerea), huia (Heteralocha acutirostris), native thrushes (Turnagra tanagri and T. crassirostris), stitch-bird (Pogonornis cincta), kakapo (Stringops habroptilus), native quail (Coturnix nova-zealandia), and the white heron (Herodias timoriensis). In addition, several species of originally very limited distribution (e.g. Stephens Island Wren and Chatham Island Fern-Bird) are now quite extinct.

Others which were abundant have been driven back into areas where settlement has not yet penetrated to any great extent1.

It must not be supposed that it is the introduced animals alone which have produced this effect, even though rats, cats, rabbits, pigs, cattle, stoats and weasels, as well perhaps as some kinds of introduced birds, have penetrated beyond the settled districts. It is largely the direct disturbance of their haunts and breeding places, and the interference with their food supply, which has caused this destruction and diminution of the native fauna.

What is true of birds is equally true of other groups of animals, though it is more difficult to arrive at the facts. Many insects which were common in the bush fifty years ago must have been displaced and have largely disappeared. I cannot appeal to figures, but the surface burning of open land which prevailed, especially in the South Island, and the wanton destruction and burning of forest which has marked so much of the North Island clearing, must have destroyed an astonishing amount of native insect life, and made room for introduced forms. The clearing of the surface for cultivation and grazing, the draining of swamps, and the sowing down of wide areas in European

1 They include the following sixteen species: native robins (Miro albifrons and M. australis), saddle-back (Creadion carunculatus), fern-bird or grass-bird (Sphenœacus punctatus), native canary (Mohua ochrocephala), tui (Prosthemadera novæzealandia), kaka (Nestor meridionalis), parakeets (Cyanorhamphus novæ-zealandiæ and C. auriceps), kiwis (Apteryx mantelli, A. australis, A. oweni and A. haastii), laughing owl (Sceloglaux albifacies), Mo-pork (Ninox novæ-zealandiæ), and native pigeon (Hemiphaga novæ-zealandia). In some settled localities, such as the neighbourhood of Wellington, Mo-porks are still met with.

pasture plants, have all contributed to this wholesale destruction and displacement of indigenous species. The disappearance of mosquitoes and sand-flies in settled districts where they were formerly very common is a case in point;-where they disappeared, it is tolerably certain other species not so well known became scarce at the same time. Unfortunately accurate data are not obtainable, for at the time that settlement began, very little was known of the insect fauna as I have shown, and even now, as already stated, whole groups are imperfectly known.

The introduction of many insectivorous birds, including pheasants, quail, starlings, minahs, species of Fringillidæ, and others, must also have accounted for the destruction of immense numbers of insects. At one time the wide tussock-covered hills and plains of both islands were just alive with grasshoppers, and in the summer months they sprang up before the pedestrian literally in thousands. To-day they are rare over wide areas where formerly they abounded. Fereday wrote in 1872:

In the early days of the Canterbury Settlement quails, larks and other birds that fed upon insects and their larvæ abounded on the plains, but the quails have been exterminated, the larks have become comparatively scarce, and the other birds have almost disappeared. So long as the plains remained open and uncultivated, extensive grass fires, sweeping over the land consumed an enormous amount of insect life, and took the place of the counter-check which was being removed by the decrease of the birds; but within the last few years inclosures and cultivation have been rapidly extending around Christchurch, and forming a nursery for the preservation and increase of the insect race. A luxuriant and abundant vegetation has sprung up for its food and shelter, and it is comparatively freed from the ravages of fire and the attacks of its feathered foes.

Lizards (especially Naultinus elegans, N. grayi and Lygosoma moco) were also extremely common in the open country fifty years ago, but are now comparatively rare. Burning the surface growth is largely responsible for their destruction, but the abundance of wild cats, which in some parts are encouraged as counteracting to some extent the rabbit pest, is also accountable for many.

The introduction of species of Salmonidæ, of perch, carp, etc., into the lakes and rivers of most parts of the country has produced equally important changes. Some species of fish have been exterminated wherever the introduced forms have established themselves, e.g. native grayling (Prototroctes oxyrhynchus), kokopuru, minnow, etc. (species of Galaxias), and smelt (Retropinna richardsoni). Similarly the native species of crayfish (Paranephrops planifrons, P. zealandicus and P. setosus), shrimp (Xiphocaris curvirostris), and species of freshwater Amphipoda, have been eaten out in streams stocked with trout.