THEORIES AS TO THE OKIGIN OF LIFE. 83 



and then the two sexes are perfected, either in 

 the same or in different individuals (as the case 

 may be), by the union of which the same cycle 

 may begin again, with similar successive changes 

 of larval development. But in cases such as 

 these, there is no specific change in the perfect 

 animals. They are of the same species with the 

 parents from which they originally sprang, and 

 though they may originate once again a most 

 complicated series of organic changes, yet all 

 such changes are governed by stern laws, where- 

 by they are resolved into cycles, and in the 

 end produce but another repetition of the old 

 animal forms." 



" If animals, from the first appearance of 

 their nascent germs to their full specific ma- 

 turity, exhibit a cycle of organic changes, what 

 is the beginning of the cycle ? What are the 

 conditions of generation ? It is the union of a 

 spermatozoon with the germinal vesicle of an 

 ovum. And these two (the spermatozoon and 

 the ovum) are the organic products of two per- 

 fect animals male and female. These condi- 

 tions being satisfied, there commences that cycle 

 of changes, which, however complicated, are de- 

 fined by the constant laws of nature, whereby 



