that the superior part of the vitellus, or the hemisphere which regards the ovary, is almost free from any contact or cohesion with the peduncle, in the superior part of the cup or hollow of which nevertheless, but somewhat to the side, the spot or cica- tricula in question is placed. The peduncles becoming detached from the vitelli can therefore in no way be said to leave any trace of their attachments behind them. Of the great importance of this spot in generation I have already spoken in the historical portion of my work.
But I have still, always following my old teacher Fabricius as my guide on the way, to treat of the uses of the cavity in the blunt end of the egg.
Fabricius enumerates various conveniences arising from this cavity, according to its dimensions. I shall be brief on the subject : it contains air, and is therefore useful in the ventila- tion of the egg, assisting the perspiration, refrigeration, and respiration, and finally the chirping of the chick. Whence this cavity, small at first, is larger by and by, and at last becomes of great size, as the several offices mentioned come into play.
Thus far have we spoken of the generation of the egg and chick, and of the uses of the several parts of the egg ; and to the type exhibited we have referred the mode of generation of oviparous animals in general. We have still to speak of the generation of viviparous animals, in doing which we shall as before refer all to a single familiarly known species.
EXERCISE THE SIXTY-SECOND.
An egg is the common origin of all animals.
" Animals," says Aristotle, 1 " have this in common with vegetables, that some of them arise from seed, others arise spon- taneously; for as plants either proceed from the seed of other plants, or spring up spontaneously, having met with some pri- mary condition fit for their evolution, some of them deriving their nourishment from the ground, others arising from and living on other plants ; so are some animals engendered from cognate forms, and others arise spontaneously, no kind of cognate
1 Hist. Anim. lib. 5, cap. 1.
