338 THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 



of S. punctulatum Breb., and we therefore call it .S'. punctulatum- 

 Breb. var. coronatum (Schmidle) nob. It is a common thing for 

 the angles of the two semicells in both S. puvctnUitum and *S'. yn/r/- 

 mmum to alternate with each other, and not uncommonly the angles 

 of the two semicells in -S'. aJternans are opposite. The figures of 

 S. alternans and S. dilatatum in Ralfs' Britisk Desmidme are amongst 

 the most beautiful and most accurate in the whole book, and are 

 exactly like thousands of specimens we have seen from all over the 

 British Isles. 



S. bicorne Hauptfl. ? Borge (IJiJiinui till K. Sv. vet.-akml. Jiandl. 

 Band 21, afd. iii. p. 24, fig. 15). This is S. Pseudosehaldi Wille, 

 ■'■Duaceitse West [Journ. Linn. Soc. (Bot.) xxix. p. 184, t. xxiv. 

 fig. 1 (1892). 



S. PROTRACTUM Kacib. [Flora, Ixxxi. p. 34, taf. iii. u. iv. fig. 14 

 (1895) ). This seems to us very like a large form of S. Ucvispinuni 

 Ijissett. 



THE DISPLACEMENT OF SPECIES IN NEW ZEALAND. 



By T. Kirk, F.L.S.'= 



In the absence of civilization, the indigenous fauna or flora of 

 any country is liable to little or no change from external causes. 

 Aerial and marine currents may occasionally bring spores or even 

 seeds of exotic plants ; more rarely, insects or birds may be intro- 

 duced by gales of unusual violence ; migratory or aquatic birds may 

 introduce the eggs of insects, or even molluscs, as well as seeds and 

 fragments of terrestrial or lacustrine plants which have become 

 attached to their feathers ; and certain terrestrial or fluviatile 

 molluscs may be introduced by drifted logs ; but after a certain 

 time any increase in the number of species by agencies of this kind 

 must become extremely rare, and can occur only at distant intervals. 

 It may therefore be concluded that in all probability the constituents 

 of the fauna and flora of this colony, with possibly the exception of 

 the larger Ratite birds, were in much the same condition when they 

 were first seen by Cook and Vancouver as they had been for many 

 previous centuries. But with the advent of civilization vast and 

 far-reaching changes speedily take place : axe and fire rapidly alter 

 the face of the country ; portions of the forest are felled, burnt off, 

 and replaced by grass — a change which of itself involves a multitude 

 of other changes ; the unfelled portions of the forest are laid open 

 to violent winds, so that the surface-rooting trees are blown over in 

 large numbers, while the increasing dryness of the atmosphere acts 

 unfavourably on the undergrowth, which is still further injured by 

 the depredations of cattle ; gradually the plants less able to resist 

 changed conditions disappear, and with them many insects, lizards, 



* Extracted from his Presidential Address to the Wellington Philosophical 

 Society, 3rd July, 1895. 



