NOWLIN : THE VITELLINE BODY IN SPIDER EGGS. 283 



The position first occupied by the latter sort of diffused yolk 

 nuclei would connect them with another class, the third and 

 last of the deutoplasmic formations in the egg-cell. This is the 

 single body which first arises as a crescent closely applied to 

 the nucleus and later moves out from this membrane, becoming 

 spherical in shape. Von Wittich was the first to investigate 

 this body. In 1845 he observed it in the spider egg, and made 

 a careful study of it in Tegeneria domestica. Balbiani (1) has 

 perhaps done more work on this structure than any other one 

 man. He made investigations upon both spider and myriapod, 

 eggs and found similar structures in them. In his paper 

 " Centrosome et Dotterkern " he compares and identifies the 

 two bodies. 



He believed the yolk nucleus or "noyau vitellin" contained 

 at its center the centrosome. In Geophilus (1) he found dis- 

 tinct radiations from that body which convinced him of the 

 nature of the central sphere. In the spider he found no radia- 

 tions, but the two formations agreed in other respects, and he 

 concluded that in this class of animals, too, the yolk nucleus or 

 vitelline body holds the centrosome. Munson (6) has de- 

 scribed in much detail the egg of Limulus. He finds, also, the 

 vitelline body there and compares it with that in Geophilus. Its 

 position against the nuclear membrane, its striated outer wall, 

 and its radiations are all similar. Munson believes the vitelline 

 body of Limulus contains a centrosome. 



The diffused yolk nuclei have been found by Jordan in am- 

 phibian eggs. Both the diffused and the single body, or vitel- 

 line body of Balbiani, have been found in mammals and birds 

 (Mertens, 7), and in Limulus (Munson, 6). Whether these 

 two apparently different classes of formations are essentially 

 the same is a question to be solved by further investigation 

 and comparison of different forms. The origin of the large 

 vitelline body, as well as its fate, has been so variously given 

 that nothing certain can be deduced. Largely for this reason 

 its exact mission is unknown. Some have given it a very 

 prominent place in the cell, believing it to be coordinate with 

 the nucleus. Henneguy (6) compares it to the macronucleus 

 of the Infusoria. 



