ON GENERATION. 251 



"In all, nevertheless, even those that lay perfect eggs, the first 

 conception grows whilst it is yet invisible ; and this, too, is the 

 nature of the worm." 1 For there is this difference between the 

 generation of worms and of other animals, that the former ac- 

 quire dimensions before they have any definite form or are dis. 

 tinguished into parts, in conformity with what the philosopher 2 

 says in the following sentence : " An animal is fashioned from an 

 entire worm, not from any one particular part, as in the case of 

 an egg, but the whole increases and becomes an articulated 

 animal," i. e. in its growth it separates into parts. 



It is indeed matter worthy of admiration, that the rudiments 

 of all animals, particularly those possessed of red blood, such as 

 the dog, horse, deer, ox, common fowl, snake, and even man 

 himself, should so signally resemble a maggot in figure and 

 consistence, that with the eye you can perceive no difference 

 between them. 



Towards the end of the fifth day or the beginning of the 

 sixth, the head is divided into three vesicles : the first of these, 

 which is also the largest, is rounded and black; this is the eye, 

 in the centre of which the pupil can be distinguished like a 

 crystalline point. Under this there lies a smaller vesicle, con- 

 cealed in part, which represents the brain ; and over this lies 

 the third vesicle, like an added crest or rounded summit crown- 

 ing the whole, from which the cerebellum is at length produced. 

 In the whole of these there is nothing to be discovered but a 

 little perfectly limpid water. 



And now the rudiment of the body, which we have called 

 the carina, distinctly proclaims itself to be the spinal column, 

 to which sides soon begin to be added, and the wings and the 

 lower extremities present themselves, projecting slightly from 

 the body of the maggot. The venous conduits are, further, 

 now clearly referrible to the umbilical vessels. 



1 De Gener. Animal, lib. iii, c. 9. 2 Hist. Anim. lib. v, c. 19. 



