ANIMALS. 369 



Bat, however inferior this kind of generation 

 may be, the observation of it will afford great in- 

 sight into that of nobler animals, as we can here 

 watch the progress of the growing embryo, in 

 every period of its existence, and catch it in those 

 very moments when it first seems stealing into 

 motion. Malpighi and Haller have been parti- 

 cularly industrious on this subject ; and, with a 

 patience almost equalling that of the sitting hen, 

 have attended incubation in all its stages. From 

 them, therefore, we have an amazing history of 

 the chicken in the egg, and of its advances into 

 complete formation. 



It would be methodically tedious to describe 

 those parts of the egg which are well known 

 and obvious, such as its shell, its white, and its 

 yolk ; but the disposition of these is not so ap- 

 parent. Immediately under the shell lies that 

 common membrane, or skin, which lines it ou the 

 inside, adhering closely to it every-where, except 

 at the broad end, where a little cavity is left, that 

 is filled with air, which increases as the animal 

 within grows larger. Under this membrane are 

 contained two whites, though seeming to us to 

 be only one, each wrapped up in a membrane of 

 'its own, one white within the other. In the 

 midst of all is the yolk, wrapt round likewise in 

 its own membrane. At each end of this are two 

 ligaments, called clialazce, which are, as it were, 

 the poles of this microcosm, being white dense 

 substances, made from the membranes, and serv- 

 ing to keep the white and the yolk in their places. 

 It was the opinion of Mr Derham, that they 



VOL. i. A a 



