158 Transactions.— Zoology. 



The great disparity in size of individuals of the same species 

 may be due to several causes. Worms living in rubbish-heaps 

 and accumulations of decayed matter not reduced to soil are 

 better nourished and less liable to checks — such as dry, cold, 

 or hot weather — than worms living in ordinary garden-soil. 

 The same remark applies to native worms living in districts 

 where the soil they inhabit is deeper, and where the rainfall is 

 annually greater. The decayed vegetable matter on which 

 introduced worms thrive well is much more nutritious and 

 more easily assimilated during digestion than garden-soil. 

 The finely-developed worms living in and subsisting on the 

 decayed humus are generally paler than others inhabiting 

 any garden-soil. I hope in the near future to ascertain the 

 exact period of growth of several species of worms from the 

 time of emergence from the cocoon to maturity. 



When describing the mode of escape of the young of Octo- 

 chcBtus multi'porus from the cocoon''' I stated that the cocoons 

 generally burst longitudinally. There are, however, some from 

 which the worm escapes leaving a round hole at the end of 

 the cocoon without rupturing the side. The cocooia-tissue is 

 drawn out a little at the thicker end, which opens around the 

 young worm's body while escaping. The head is protruded 

 first, and the young worm slowly emerges. When the young 

 worm is of large size the cocoon ruptures along the side and 

 allows it to escape more easily. In a few instances we have 

 observed them emerge in a doubled position. In the months 

 of July and August we collected cocoons of Lumbricus pur- 

 piireus, L. terrestris, L. ruhellus, and Microscolex modestns. 

 In the first-mentioned species the young emerged from the 

 cocoon in three and four hours. The young of some of the 

 three last named required from six to twenty-four hours. The 

 cocoons of 0. multiporus and A. roses are about equal in size. 

 The recently-emerged worms are, however, distinguished by 

 the latter becoming pale-brown in a few days. 



Extinction of Endemic Eartlncorms. — When tussock land is 

 first broken up great numbers of the larger species of worms 

 {Acanthodrili) are torn to pieces or otherwise injured by the 

 plough, and die from the effects. If the land is afterwards 

 ploughed for a few years in succession very few full-grown 

 worms escape destruction — in fact, wherever the land is well 

 cultivated, whether in fields or gardens, the native earthworms 

 disappear in a few years. So long as the native land remains 

 in its naturally solid and rich condition alien worms avoid it, 

 and are very rarely found in it. When once ploughed the 

 natural freshness and loosening of the soil promotes a 

 vigorous growth of introduced plants, which soon impover- 



• Traifs. N.Z. Inst., vol. xxv., p. 115. 



