Smith. — Notes on New Zealand Earthworms. 113 



Venezuela, castings, probably ejected by a species of Urochata, 

 are common in the gardens and fields, but not in the forests, 

 as I hear from Dr. Ernst, of Caracas."* In the forests of 

 Westland I was unsuccessful in finding a single casting, except 

 where the bush had been cleared, and trodden by cattle. In 

 the more remote untrodden bush the roots of ferns and 

 mosses, of seedling and sapling trees and shrubs, form a dense 

 network of considerable depth, in which worms do not appear 

 to exist. We found them occasionally under fallen and 

 decayed logs, and they are exceedingly numerous in the dark- 

 coloured subsoil underlying the debris and roots of the forest. 

 The subsoil in many parts is extremely rich, and doubtless 

 formed the original surface mould of the country before the 

 now magnificent forest spread over it. The small bush-clear- 

 ings made by settlers are soon compressed by cattle, and in a 

 few years the castings of earthworms are ejected plentifully 

 on the surface. In the valley of the Grey Biver the older 

 bush-clearings produce a rich growth of English grasses, and 

 worms are plentiful in the soil. "Where well-trodden paths or 

 land exist their castings abound in great numbers. When 

 digging for specimens we observed the varying depths of the 

 superficial mould overlying the original layer of forest debris. 

 Some of the clearings are twenty and twenty-five years 

 cleared, and several of the sections we examined showed 

 distinct layers of surface-soil, varying from Tin. to llin. in 

 depth. The original layer of forest mould was distinctly 

 traceable, which also varied considerably in depth. This rate 

 of accumulation of mould is greater than any results given by 

 Darwin, at least during the period of time it accumulated. 

 If, however, we consider the extremely humid and mild 

 climate of Westland generally at all seasons of the year, the 

 result is perfectly reconcilable. Darwin's researches on the 

 accumulation of mould by earthworms were carried on in 

 England, which country cannot compare with the mild and 

 humid climate of Westland, at least in the natural conditions 

 favourable for the actions and increase of worms. 



The introduction, great increase, and rapid dispersion of 

 alien forms may be briefly discussed here. No doubt the 

 several species of British and other exotic worms now common 

 in New Zealand have been introduced at various times in the 

 soil of plant-cases, and in the soil used as ships' ballast. The 

 phenomenal increase of aliens is due chiefly to the genial 

 climate, and to the absence of their natural enemies. The 

 rich land in many parts of the country is also very favourable 

 to their increase. The rapid dispersion of introduced worms 

 is due to the distribution of trees and shrubs from nurseries, 



* "Vegetable Mould," p. 123. 



