360 THE INDUCTIONS OF BIOLOGY. 



facts just instanced. Defence of it involves the assertion 

 that where buds arise, normal or cauline, there exist in due 

 proportion the various ids with their contained determinants 

 that these are diffused throughout the growing part of the 

 soma ; and this implies that the somatic tissue does not differ 

 in generative power from the germ-plasm. 



The hypothesis of physiological units, then, remains out- 

 standing. For cauline buds imply that throughout the plant- 

 tissue, where not unduly differentiated, the local physiological 

 units have a power of arranging themselves into the structure 

 of the species. 



But this hypothesis, too, as it now stands, is inadequate. 

 Under the form thus far given to it, it fails to explain some 

 accompanying facts. For if the branch just instanced as 

 producing a cauline bud be cut off and its end stuck in the 

 ground, or if it be bent down and a portion of it covered 

 with earth, there will grow from it rootlets and presently 

 roots. The same portion of tissue which otherwise would 

 have produced a shoot with all its appendages, constituting an 

 individual, now produces only a special part of an individual. 



97c. Certain kindred facts of animal development may 

 now be considered. Similar insufficiencies are disclosed. 



The often-cited reproduction of a crab's lost claw or a 

 lizard's tail, Mr. Darwin thought explicable by his hypo- 

 thesis of diffused gemmules, representing all organs or their 

 component cells. But though, after simple amputation, re- 

 growth of the proximate part of the tail is conceivable as 

 hence resulting, it is not easy to understand how the remoter 

 part, the components of which are now absent from the 

 organism, can arise afresh from gemmules no longer origin- 

 ated in due proportion. Prof. Weismann's hypothesis, again, 

 implies that there must exist at the place of separation, a 

 ready-provided supply of determinants, previously latent, 

 able to reproduce the missing tail in all its details nay, 

 even to do this several times over : a strong supposition ! 



