94 TEE ZOOLOGIST. 



result of these and that which we might expect to be the out- 

 come of less sudden variations (indefinite), and, moreover, the 

 apparently graduating decline of fertility in the evoluting 

 species given in the table of hybrids seems to render unlikely 

 any such explanation as the above architectural theory suggests. 



Any violent or abrupt change of germ-plasm seems in the 

 face of these graduating results to be unusual, although one 

 must admit this graduating evolution of germ-plasm is revealed 

 in what appears to the eye as very apparent jumps as regards 

 the outward form. However, are not the long-haired cavies as 

 fertile with individuals of the parent type as these latter 

 normally are inter se ? and also the fertility of crosses of Zebu 

 and European cattle, surely mutants showing a difference 

 sufficiently great in jumping power to illustrate my meaning as 

 to the congeniality of the germ-plasm as contrasted with the 

 divergence of the outward form of these types. On the other 

 hand, this graduating germ-plasm theory does at times receive 

 a nasty jar, as notably in the instance of the beetle Leptinotarsa 

 rubicunda, but perhaps I had better refer to this later on, and 

 merely state now that, although this example seems at variance 

 with our graduation theory of the germ-plasm, it is not unlikely 

 that in some cases this jump in the plasm does take place ; that 

 the plasm does at times arrive more quickly at an uncongenial 

 stage than appears general. This need not, however, force us 

 to accept any such improbability or probability as an architec- 

 tural physiological unit. 



There is, of course, the question of blood parasites to be 

 considered as bearing on sterility, which has been put forward as 

 the cause of the sterility of certain species, such as some of the 

 bison herds which show unsatisfactory breeding results. Upon 

 matters such as these, and others such as the sterility of human 

 races as the Tasmanians, one loses oneself in conjecture. The 

 sudden sterility of the Tasmanians, for instance, appears, if not 

 attributal to blood parasites or inbreeding, to be almost super- 

 natural, psychological perhaps. 



Another point, in which I imagine the more correct relation- 

 ships of animals from similarity of germ-plasm as against 

 structural changes are shown, is from the resemblance in the 

 generative organs found in the various orders. While nutri- 



