"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.
