NOWLIN : THE VITELLINE BODY IN SPIDER EGGS. 293 



of equal age, and if not developing this one at the cost of the 

 others, at least giving it much advantage in point of time. 

 (Fig. 7, pi. XII.) 



The location of the oocyte changes as it grows, the cell 

 moving more and more to the periphery of the tube, pushing 

 through the epithelial lining, and finally through the muscu- 

 lar coat upon the exterior. (Fig. 6, pi. XII.) Its connection 

 with the tube is not severed, however, for it has not broken 

 the peritoneal coat. It has merely pushed this before it 

 through the opening it has made in the muscular wall. Be- 

 sides this means of preserving its relation to the ovary, it has a 

 more efficient one still : a small mass of epithelial cells seems 

 to follow in the track of the egg and to attach one point of 

 its periphery. These cells are pulled partly out through the 

 opening, causing them to appear as a neck holding the oocyte 

 in place. Their real mission is doubtless to convey nourishment 

 from the interior of the ovary to the growing oocyte, which 

 needs such quantities at this period in its development. 



The appearance of the nucleus during this progress does not 

 materially change. While the oocyte is in the tube the nucleus 

 contains little chromatin, and this almost immediately begins 

 to collect together. (Fig, 7, pi. XII). The cytoplasm is scanty 

 and is scattered irregularly through the cell. 



From this time the egg is most interesting in its develop- 

 ment. The wall around it becomes thicker and firmer, yet does 

 not lose its elasticity ; for rapid growth takes place, enlarging 

 and expanding constantly the outer membrane. The cytoplasm 

 of the egg is no longer clear, but there seems to be an inpour 

 of material clouding the cell and forming in certain parts of it 

 a dense zone. There appears about this time, too, the peculiar 

 element known as the vitelline body, the growth and develop- 

 ment of which is unique. These things will be dealt with in 

 detail later, so I merely mention them here. 



As the cell grows the nucleus increases in size, becoming 

 richer in chromatin. It possesses always one very large nucle- 

 olus, and very often three or four smaller bodies. The nucle- 

 olus is always vacuolated and the small bodies lying near have 

 very much the appearance of being given off from it, as Balbi- 

 ani described in his work on Tegenaria. Occasionally there 

 may be seen inside the nucleolus very dense opaque bodies or 



