384 A. J. GOLDFARB. 



etc. In eggs, physiologically poor at the time of liberation, there 

 is either a short period of acceleration, part B, followed by a long 

 period of retardation, parts C, D, E, etc. In eggs in still poorer 

 condition, the retardation takes place from the very beginning 

 of the experiment, parts C, D, E, etc. Hence the better the 

 condition of the eggs the longer the membrane-forming period 

 and the longer the period of acceleration. The poorer the con- 

 dition the shorter the periods. 



I have chosen the reciprocal curve, for in this form it becomes 

 quite clear that it is identical with Fig. I, showing increase in 

 size of eggs, and decreased per cent, of jelly layers, with age. 

 I will discuss this correlation later. 



There is one other matter that deserves brief mention. It was 

 observed repeatedly that physiologically good eggs form mem- 

 branes a considerable distance from the egg surface. With 

 increasing age and with change in rate of membrane formation, 

 the membranes are formed closer and closer to the egg, until 

 they could barely be distinguished from the plasma membrane, 

 and finally did not appeal at all. With this reduction in width 

 of the perivitelline space there appeared to be a greater tendency 

 toward scalloping or blistering in the early appearance of the 

 membrane. The Hertwigs in '86 observed a similar narrow 

 perivitelline space and scalloping in ageing eggs. 



Arbacia. 



Some observations upon Arbacia eggs gave similar results, 

 with one exception, namely, there was no initial acceleration of 

 rate in membrane formation so characteristic of Toxopneustes. 

 But this lack of acceleration may however have been due to 

 insufficient early observations. The facts are brought together 

 in Table 1 1. b. 



In experiment I (Table 1 1. b), the eggs of 2 out of the 5 females 

 that formed membranes at all, after the first observations, showed 

 retardation in rate with age. 



In experiment 3, the eggs of 4 out of the 7 females that formed 

 membranes after the first observation, also showed retarded rate 

 of membrane formation. 



In experiment 2, one female showed retardation, another 



