OF THE FOETUS. 311 



quantity of the male fluid. The eggs in the ova- 

 rium of oviparous females are analogous to the 

 glandulous bodies in the teflicles of the vivipa- 

 rous : The cicatrice of the egg correfponds to 

 the cavity of thofe glandulous bodies which con- 

 tain the female femen ; and that of the male 

 penetrates and mixes with it- Tlie formation ot 

 the embryo inftantly refults from this mixture 

 or union of the two fluids. The firft -egg laid 

 by the hen after her communication with the 

 cock is fecundated, and capable of being hatch- 

 ed. Thofe which (he is afterwards to lay were 

 all impregnated at the fame inftant : But, as 

 they want fome efiential parts, the produdlion 

 of which has no dependence on the male fluid ; 

 as they have neither the white, the membranes, 

 nor the fliell, the imall embryos contained in 

 ,the cicatrices of thefe imperfed: eggs, are inca- 

 pable of being hatched, though aided by the in- 

 ternal heat of the mother. The em.hryo, there- 

 fore, remains in the cicatrice in the fame flate in 

 which it was firft formed, till the egg acquires 

 all the parts neceflliry to the growth and nou- 

 liflament of the foetus ; and it is not till afrer 

 the egg has arrived at fidl perfeQion, that the 

 expanfion of the embryo commences. This cx- 

 panfion is effcded by the external heat of incu- 

 bation : But it is unqucftionable, that, if the egg 

 could be retained in the body 21 days after it 

 was (Completely formed, the chick would be 

 Jjatched, unlefs the internal heat of tlie mother 



were 



