EPIGENESIS OR EVOLUTION. 107 



a tolerably strong resemblance to some of the most recent 

 theories that have been put forward. 



In estimating the value of the doctrines of the older 

 biologists this fact should not be lost sight of, that for want 

 of good microscopes and of proper methods of microscopical 

 investigation, they were very far from having those clear 

 and definite conceptions of minute structure which we now 

 possess. The conclusions to which they arrived may have 

 been, indeed they often were, very ingenious and acute, but 

 the want of definite ideas of cell structure and cell division, 

 and, above all, the want of a sufficient number of instances 

 taken from all parts of the animal kingdom, is apt to lead 

 us to underestimate the value of their generalisations when 

 compared with the very similar results obtained in the pre- 

 sent day. It is certainly a striking fact that the most 

 minute and elaborate researches of the last few years have 

 led the course of biological speculation back to the point of 

 view of Haller and Bonnet in the eighteenth century, and 

 have threatened to discredit altogether the opposite doctrine 

 of epigenesis, which, as the result of the cell theory of 

 Schleiden and Schwann, and the accumulated work of 

 embryologists from the time of Von Bar and Rathke 

 onwards, seemed to be triumphant all along the line. 



The doctrine of epigenesis, really due to Aristotle, but 

 elaborated and definitely propounded by Harvey, is simply 

 a statement of the observed and observable facts in the 

 ontogeny of any multicellular organism. In the egg, what- 

 ever may be its shape in its mature condition, one cannot, 

 by any optical aid or chemical methods, recognise any 

 structure more complex than that which is characteristic of 

 a simple cell. This is an incontrovertible fact which has 

 over and over again been insisted upon, and in spite of the 

 recent additions to our knowledge of cell structure, the same 

 statement which was made, and more than once repeated 

 in Balfour's Embryology, holds as good to-day as it did ten 

 years ago, namely, "that the ovum in its young condition 

 is obviously nothing but a simple cell, and such it remains 

 till the period when it attains to maturity ". The circum- 

 stance that we are now able to recognise in the ovum several 



