What Aristotle says on the subject of the reproduction of the chick in ovo is perfectly correct. Nevertheless, as if he had not himself seen the things he describes, but received them at second hand from another expert observer, he does not give the periods rightly; and then he is grievously mistaken in respect of the place in which the first rudiments of the egg are fashioned, stating this to be the sharp end, for which he is fairly challenged by Fabricius. Neither does he appear to have observed the commencement of the chick in the egg; nor could he have found the things which he says are necessary to all generation in the place which he assigns them. He will, for instance, have it that the white is the constituent matter (since nothing naturally can by possibility be produced from nothing.) And he did not sufficiently understand how the efficient cause (the seminal fluid of the cock,) acted without contact; nor how the egg could, of its own accord, without any inherent generative matter of the male, produce a chick. Aldrovandus, adopting an error akin to that of Aristotle, says besides, that the yelk rises during the first days of the incubation into the sharp end of the egg, a proposition which no eyes but those of the blind would assent to; he thinks also that the chalazæ are the semen of the cock, and that the chick arises from them, though it is nourished both by the yelk and the white. In this he is obviously in opposition to Aristotle, who held that the chalazæ contributed nothing to the reproductive powers of the egg. Volcherus Coiter is, on the whole, much more correct; and his statements are far more consonant with what the eye perceives. But his tale of the three globules is a fable. Neither did he rightly perceive the true commencement of the chick in ovo. Hieronymus Fabricius contends that the chalazæ are not the sperma of the cock; but then he will have it that “from these, fecundated by the seminal fluid of the cock, as from the appropriate matter, the chick is incorporated.” Fabricius observed the point of origin of the chick, the spot or cicatricula, namely, which presents itself upon the tunica propria of the yelk; but he regarded it as a cicatrice or scar left on the place where the peduncle had been attached; he viewed it as a blemish in the egg, not as any important part. Parisanus completely refutes Fabricius’s ideas of the chalazæ; but he himself obviously raves when he speaks of certain circles, and principal parts of the fœtus, viz., the liver and heart. He appears to have observed the commencement of the fœtus in ovo; but what it was he obviously did not know, when he says, “that the white point in the middle of the circles is the semen of the cock, from which the chick is produced.”