314 EMBRYOLOGY 



cell is a self-sufficient whole, and because I cannot conceive how a 

 new species can arise if this view is well founded. As is a tissue-cell 

 to a germ-cell, so is a germ-cell to ancestral germ-cells. If tissue-cells 

 are out of the line of descent to new generations, and predestined for 

 their parts in individual history, so must germ-cells be predestined 

 for their parts in ancestral history, and out of the line of descent to 

 anything strictly new; but the notion that the conduct of the breeder 

 of carrier-pigeons and fantails and tumblers was predestined in the 

 germ-plasm of the rock pigeon carries Calvinism to giddy heights that 

 I cannot scale. 



Other zoologists tell us that, since the germ-cell is formed by a pro- 

 cess which may be regarded as modified fission, it is fundamentally 

 symmetrical with the body that produced it, and its axes and poles 

 coincident with those of the parent, so that it is practically equivalent 

 to a complete organism from the first, so far as its stereometry or 

 promorphology is in question. This doctrine may, perhaps, rest on a 

 basis of fact, but it gives no account of the stereometry of the parent. 



Others, who agree that the organism is a unit, a complete whole, 

 a specific being, from the egg onwards, assert that, while cellular differ- 

 entiation may enable us to infer organization, it is a serious error to 

 regard it as the measure, or the means, of organization; that the egg 

 is young organism, and not a mere germ that is to become an organ- 

 ism; that there is no qualitative or essential difference between an 

 unicellular and a multicellular organism, between an unicellular 

 germ and the being that arises from it; and that, while complexity 

 increases as development progresses, division into cells is not the 

 means, but only the indication of its progress. There seems to me to 

 be a basis of truth for this doctrine also, but when its advocates tell 

 us that the species is contained in the hen's egg as completely as it 

 is in the hen, their words seem to me to be meaningless, because I 

 have learned from Darwin that the species is neither in the egg nor in 

 the hen, since it is in that reciprocal interaction between the living 

 being and the world around it which I have learned to call the struggle 

 for existence. 



Thus the current literature of embryology brings us back to the 

 question we had agreed to lay aside, whether development is inherent 

 in the egg or induced by the conditions of its life. 



It may interest you to know what an old question this is. More than 

 two hundred and fifty years ago, that great man of science, William 

 Harvey, declared his intention to "seek the truth regarding the follow- 

 ing difficult question : Which and what principle is it whence motion 

 and generation proceed? Whether is that which, in the egg, is cause, 

 artificer, and principle of generation, innate or superadded? Whether 

 is that which transfers an egg into a pullet inherent or acquired? 

 In truth," says he, "there is no proposition more magnificent to 



