EARLIEST PERIOD OF GROWTH. HI 



There is one fact, moreover, that must not be forgotten ; it is 

 this, that all animals, from the monad, the gum-drop Ama'ba, up 

 to man, at one time cannot possibly be distinguished from one an- 

 other ! I mean in the earliest egg-state. When I described to 

 you the other night the manner of development of the egg, I 

 showed that all eggs (page 33) commence as a mere drop of 

 fluid, with certain bipolar characteristics. Now whether this drop 

 of fluid be taken from the Amosba, the coral, the worm, the shell- 

 fish, or the rabbit, you could not tell the one from the other, any 

 more readily than you could distinguish a drop of water from Co- 

 chituate Lake from that of Mystic River! The distinguishable 

 characteristics appear in the process of time and development. 



Now, when I say that all animals, from the monad up to man, 

 at one time cannot possibly be distinguished, per se, from one 

 another, I mean to draw your attention to another fact, which is, 

 that all animals at one time are as simple as those which are thus 

 far known to arise by spontaneous generation. The higher ani- 

 mals do not at once leap into life in a full-grown state, but they 

 arise out of as simple elements as do those lowest forms which 

 originate through spontaneous generation. The higher forms 

 pass through the same relative conditions as do the lower ones, 

 and then rise to higher states. This idea is also carried out in 

 another way, in restricted groups, as I have shown you in a pre- 

 vious lecture (p. 40) ; thus the quadruped, when in its earlier 

 stages, possesses a conformation of its principal organs that is, 

 the heart and nervous system similar to that of a fish; then 

 it takes on the form and relations of the next higher group, 

 namely, the reptiles, and then that of birds, and finally its adult 

 conformation. 



In the instance of spontaneous generation, the animals com- 

 mence these simple stages without a parent ; whereas, among 

 higher animals, their simple drop-of-fluid stage is farther removed 

 from external causes, and is subjected to parental influence as 

 a primary cause, and secondary causes affect the progeny 

 through the parent at first, and afterwards directly, when the 

 egg- animal is cast forth upon the world. In the latter case the 



