10 METAMOEPHOSES OF MAN 



fact,, which is placed beyond doubt by the further and 

 more searching investigations of these two naturalists, 

 and the splendid works of the English and German 

 physiologists, Barry, Bernhardt, Bischoff, Wharton 

 Jones, Valentin, Wagner, &c. &c. It is at present 

 satisfactorily proved, that mammals, and even man 

 himself, as well as birds and reptiles, proceed from 

 actual eggs. 



From one end to the other of the animal kingdom, 

 the structure of these latter is probably identical in 

 every essential particular. In mammalia, as in the 

 Eadiata or the Worms; in man, as in Hermella or 

 Synapta, three spheres lying one within the other, and 

 inclosed by a transparent membrane, constitute the 

 germ. To these three spheres may be added various 

 envelopes and accessory layers for their protection, or 

 to aid in supporting the new creature ; but, within the 

 vitelline membrane may invariably be found the 

 vitellns or yolk, embracing the germinal vesicle of 

 Purkinje, which itself incloses the germinal spot of 

 Wagner. 



The exact function performed by each of these 

 spheres is far from being known; but it is certain 

 that the vitellus consists of organizable and nutritious 

 matter. In some ovipara, this supply of food is ex- 

 tensive ; a small portion is sufficient for the construc- 

 tion of the new being, which is nourished and grows 

 at the expense of the remainder. The fish, for ex- 

 ample, springs from the egg completely formed. How- 

 ever, it still carries attached to its belly a large bag, 

 containing the greater part of the yolk-substance ; and 

 this being slowly absorbed, provides it with nourish- 

 ment for more than a month after it has been hatched. 



