Appendix I. 179 



tissues of an organism and its specially reproductive 

 elements. On the contrary, the microscope is able to 

 demonstrate possible roads of connexion — and this even 

 upon "VVeismann's own view as to a specialized germinal 

 substance which is restricted to the nucleus of an ovum. 

 In short, the supposition as to an absolute anatomical 

 separation between germ-plasm and somato-plasm is a de- 

 duction from Weismann's theory itself: it is not supported 

 — it is discredited — by histological observation. Hence, 

 it cannot be accepted as valid evidence in favour of the 

 theory from which alone it is derived, or as a valid 

 objection to the rival theory of pangenesis. 



Once more, even if it were true that histology proves 

 an absolute anatomical isolation on the part of germ-cells, 

 it would still have remained unquestionable that there is no 

 absolute physiological isolation. For, at least, the germ- 

 plasm derives its nourishment from the soma in which it 

 resides ; and who shall say that the process of mere imbibi- 

 tion is not amply sufficient to admit of the passage of 

 " gemmules " ? Call them what we choose, the " carriers 

 of heredity " must be so unimaginably small, that in relation 

 to histological cells they must be as gnats to camels. Yet 

 we know that even camels in the form of " migrating cells " 

 of various kinds are able to pass through living membranes ; 

 and we also know that the microbes of syphilis can 

 penetrate both ova and spermatozoa. Why then should it 

 be deemed inconceivable that, where all such things can 

 pass, gemmules can do so likewise? 



Lastly, I have recently spoken of the detached condition 

 of a ripe ovum in utero. Now it seems to me more " in- 

 conceivable " that such an ovum should be capable of 

 announcing, as it were, to the walls of the uterus whether or 

 not it is in a fertilized condition, than it is that, before quit- 

 ting the ovary, it should have had some kind of physiological 

 converse with its environing soma. Yet it is certain that, 



N 2 



