172 THE BIOLOGY OF AN ANIMAL. 



The microscopic study of the earthworm may be almost 

 indefinitely prolonged, and is of great interest. The foregoing 

 outline indicates, however, all that is necessary for the beginner. 

 The study of the embryological development is impracticable 

 for the beginner under ordinary circumstances, though at the 

 proper season and with suitable guidance it may be made inter- 

 esting and valuable. 



