150' RE GENERA TION 



budding; for, while they both involve an increase in the products 

 over that of the original animal, the axial relations in lateral buds are 

 established in a new plane, while in axial budding the main axis of 

 the new animal is a part of that of the old, and this difference may 

 involve different factors. The process of budding does not occur in 

 the insects, spiders, crustaceans, mollusks, ctenophores, brachiopods, 

 nematodes, vertebrates, or in several other smaller groups. 



This examination shows that there are groups in which both pro- 

 cesses take place, viz. ccelenterates, planarians, annelids ; and others 

 in which budding alone takes place, viz. ascidians, polyzoa, cephalo- 

 discus; and one group at least in which division, but not budding, 

 takes place, the echinoderms. It is obvious that from the occurrence 

 of the process of budding in the animal kingdom we cannot infer 

 anything as to its relation to division or to regeneration. 



It has been pointed out that in the flowering plants, in which the 

 growth takes place by means of buds, the power of terminal regen- 

 eration is very slightly developed, and its absence is sometimes ac- 

 counted for on the ground that the new growth takes place by means 

 of the development of lateral buds. If by this statement it is meant 

 that buds being present the suppression of regeneration in other 

 regions may occur, then there may be a certain amount of truth 

 in the statement. If, however, it is intended to mean that be- 

 cause a plant has acquired the power of reproducing new parts by 

 means of buds it has, therefore, lost the power to regenerate in other 

 ways (or has never developed the power to regenerate), then the 

 argument is, I think, fallacious ; for we find even in flowering plants 

 that the new buds sometimes arise from the new part, or callus, 

 that forms over the cut-end, and this process resembles a real regen- 

 erative process. We also find that hydroids that produce lateral 

 buds also regenerate freely from an exposed end. But we are at 

 present so much in the dark in regard to the causes that bring about 

 budding in organisms that a discussion of the possibilities would 

 hardly be profitable. 



AUTO TOM Y 



The process of autotomy differs only in degree from the process 

 of self-division. In autotomy the part thrown off does not produce 

 a new animal. The breaking off of the tail of the lizard at the base, 

 if the outer part is injured, is an example of a typical process of 

 autotomy. The throwing off of the crab's leg, if the leg is injured, is 

 also another typical case of autotomy. There is a definite breaking- 

 joint at the base of the crab's leg at which the separation always 

 takes place (Fig. 45, A i-i). The breaking-joint is in the middle of 

 the second segment from the base of the leg, where there is found, 



