BIOLOGICAL BEGINNINGS 3 I 



I now propose briefly to unfold that argument, and to set forth, in a 

 form intelligible to those who possess no special acquaintance with ana- 

 tomical science, the chief facts upon which all conclusions respecting the 

 nature and the extent of the bonds which connect man with the brute 

 world must be based: I shall then indicate the one immediate conclusion 

 which, in my judgment, is justified by those facts, and I shall finally dis- 

 cuss the bearing of that conclusion upon the hypotheses which have been 

 entertained respecting the Origin of Man. 



The facts to which I would first direct the reader's attention, though 

 ignored by many of the professed instructors of the public mind, are easy 

 of demonstration and are universally agreed to by men of science; while 

 their significance is so great, that whoso has duly pondered over them 

 will, I think, find little to startle him in the other revelations of Biology. I 

 refer to those facts which have been made known by the study of De- 

 velopment. 



It is a truth of very wide, if not of universal application, that every 

 living creature commences its existence under a form different from, and 

 simpler than, that which it eventually attains. 



The oak is a more complex thing than the little rudimentary plant con- 

 tained in the acorn; the caterpillar is more complex than the egg; the 

 butterfly than the caterpillar; and each of these beings, in passing from its 

 rudimentary to its perfect condition, runs through a series of changes, the 

 sum of which is called its Development. In the higher animals these changes 

 are extremely complicated; but, within the last century, the labours of 

 such men as Von Baer, Rathke, Reichert, Bischof, and Remak, have almost 

 completely unravelled them, so that the successive states of development 

 which are exhibited by a Dog, for example, are now as well known to the 

 embryologist as are the steps of the metamorphosis of the silk-worm moth 

 to the school-boy. It will be useful to consider with attention the nature 

 and the order of the stages of canine development, as an example of the 

 process in the higher animals generally. 



The Dog, like all animals, save the very lowest (and further inquiries 

 may not improbably remove the apparent exception), commences its 

 existence as an egg: as a body which is, in every sense, as much an egg as 

 that of a hen, but is devoid of that accumulation of nutritive matter which 

 confers upon the bird's egg its exceptional size and domestic utility; 

 and wants the shell, which would not only be useless to an animal in- 

 cubated within the body of its parent, but would cut it off from access 

 to the source of that nutriment which the young creature requires, 

 but which the minute egg of the mammal does not contain within it- 

 self. 



The Dog's egg is, in fact, a little spheroidal bag, formed of a delicate 

 transparent membrane called the vitelline mejiihrane^ and about Ksoth to 



