EFFECTS OF AGING UPON GERM CELLS. 373 



It was suggested that these variations served as convenient 

 and accurate indices of the physiologic condition or vitality of 

 the freshly removed eggs or sperm of different individuals. 



In the present paper the same technique, the same three 

 species of sea urchin, the same nomenclature and the same pre- 

 cautions were taken. It is proposed to determine first the phys- 

 iologic condition of the germ cells, at the time of liberation, 

 from given individuals, and then to determine the nature and 

 the extent of the changes in the eggs and sperm as they become 

 increasingly "overripe," "aged" or" stale." 1 In the next 

 study, Part III., it is proposed to study other changes that 

 appear in very late stages of overripening or ageing of the germ 

 cells. I reserve for Part III. a discussion of the entire problem, 

 and the bibliography. 



The changes that were observed in moderately aging eggs, 

 and those which will be discussed in detail are: (i) size, (2) 

 jelly layer, (3) membrane formation and (4) cleavage. 



I wish to acknowledge my indebtedness to Dr. A. G. Mayer, 

 Director of the Marine Biological Laboratory of the Carnegie 

 Institution of Washington, and to Prof. F. R. Lillie, Director of 

 the Marine Biological Laboratory at Woods Hole, Mass., for the 

 opportunity of working on this problem at their respective 

 laboratories, and for the many facilities offered in connection 

 with this work. 



EFFECT OF AGE UPON SIZE OF EGGS. 

 Hipponoe and Arbacia. 



The diameters of freshly removed unfertilized eggs of each 

 freshly collected female, were measured with an ocular microm- 

 eter (no. 3 eye piece and Y objective) and the usual pre- 

 cautions concerning pressure, focusing, sampling, etc., taken. 

 At different intervals (ages) other samples of the eggs of the 

 same female were measured. The data are brought together in 

 Table I. 



I have shown (Goldfarb, '17) that the normal size of freshly 

 liberated eggs of Hipponoe varied from 18^ to 20 ocular unit 5 

 in diameter, with a mode of 19^/2 units. In the present serie s 



1 By age is meant the time since removal or extrusion of ripe germ cells. 



