NOWLIN : THE VITELLINE BODY IN SPIDER EGGS. 287 



ment as regular as clockwork the abdomen was raised and 

 lowered — raised to unravel the threads, lowered and pressed 

 firmly against the ground to fasten them. Never moving from 

 the spot, but turning around and around over the hole, the 

 little creature directed her spinnerets to every part of the bot- 

 tom, until at last it was covered with a closely woven sheet. 

 She was not content with the one layer, but spun another, and 

 then touched it carefully here and there, to detect any neglected 

 spots. When she found one, she spun diligently for some time 

 about it, until it was completely remedied. 



Then began the most interesting part of this queer perform- 

 ance. Placing the spinnerets at the edge of the white mat, she 

 began once more a monotonous turning. So many times she 

 turned and so empty the apparent result, I thought her insane 

 from her previous work. After a long wait, I realized that a 

 wall was growing, and although of such delicate and flimsy ma- 

 terial, it was rising into space, unsupported by anything the 

 eye could see. When completed, it was more remarkable still, 

 for it leaned slightly over the hole, forming a sort of hollow 

 sphere. A large opening was left at the top, however, and 

 after a pause the spider ejected two drops of colorless fluid into 

 the nest. These were soon followed by the eggs, which were a 

 golden yellow, and so numerous and of such semifluid con- 

 stituency that they were oviposited in a continuous stream. 

 When the nest was almost filled, the little animal paused once 

 more, then set about closing the opening. First she pressed 

 the edges of the cocoon carefully over the eggs, but this not 

 covering them, she began spinning once more. In a short 

 time her treasures were sealed tightly within, and pressing the 

 cocoon on all sides with the third pair of legs, she lifted it 

 with the spinnerets and carried it to the edge of the jar. 



V. TECHNICAL METHODS. 



a. Fixation. 



On account of physiological variations in the egg it was nec- 

 essary to employ several fixatives. The very young ova are 

 much more easily preserved than those further advanced ; in 

 fact, after the egg has entirely filled with yolk it is difficult to 

 get a satisfactory fixation at all. The chief cause of the trouble 

 lies in the egg-membrane. In the early follicular ova this is 



