148 EVOLUTION OF TO-DAY. 



change. Such a complete knowledge as this it is 

 useless to hope for, but every day gives a closer ap- 

 proximation to it, and it is quite probable that the 

 state of the science may reach a condition where it will 

 be possible to sketch the general history of animals. 

 A short summary of the teachings of embryology 

 is something as follows : All animals start together 

 as a single cell, so that the man cannot be distin- 

 guished from the lobster or mollusk. An embryo 

 arises from this cell, which shows itself to be a ver- 

 tebrate in distinction from an invertebrate, but is as 

 yet not a mammal, but more like a fish. With further 

 development it shows a slight approximation toward 

 the reptiles, but instead of becoming a member of 

 this class, takes a little different course and declares 

 itself to be a mammal. Next, it turns toward the 

 direction of the primates rather than rodents or 

 ungulates ; then it exhibits the characteristics of an 

 ape, in distinction from the Lemurs ; and finally, 

 just before birth, it takes on the features of man. 

 And this same story is repeated in all cases, the line 

 of development being the sub-kingdom, the class, 

 the sub-class, the order, the family, the genus, the 

 species, thus coinciding with one tree-like classifi- 

 cation of animals. While this is the general history, 

 some points demand more extended notice. 



The Abundance of Hypothetical Stages. 



Considering all of these difficulties, we are pre- 

 pared to be somewhat disappointed when we try to 

 take a general view of the positive results. The 

 positive conclusions are few, the negative conclusions 



