1 6 A. J. GOLDFARB. 



tion depended upon three factors, namely, the condition of the 

 eggs when liberated, the time after liberation (age), the tem- 

 perature. The more deteriorated the eggs at liberation, the 

 greater the rate of change at any given interval thereafter. 

 Likewise the longer the period (age) after liberation, the greater 

 the rate of change or senescence. And finally the higher the 

 temperature of the sea water, the faster the deterioration, 

 closely approximating the expectation from Van't Horf's law. 

 The sea water at the Tortugas was approximately 10 C. higher 

 than at Woods Hole, and the rate of deterioration was more 

 than twice as great in the former as in the latter. 



With further aging and increasing rate of change, other symp- 

 toms of deterioration became manifest and were increasingly 

 intensified, such as agglutination, fusion, abnormal cleavage 

 and cytolysis. These have been described and measured for the 

 three species. 



If the germ cells of other tropical organisms behave as those of 

 the two tropical species of sea urchins, i. e., die or become in- 

 infertile, or are unable to develop beyond an early stage, even a 

 few hours after liberation, one may account, at least in part, for 

 the relatively few individuals that reach maturity in so many 

 tropical species. 



The eggs that do survive show profound changes in nearly all 

 and possibly all the parts of the egg. A full appreciation of this 

 fact enables one to correlate and to find a common explanation in 

 apparently unrelated experiments. 



A number of investigators have noted a decreased productivity 

 with increasing age of the mother. Minot ('91) came to this 

 conclusion from his experiments with guinea pigs. Marshall's 

 observations upon women, Pearl's upon fowls and lambs, Ham- 

 mond's upon rabbits and pigs, and recently King's upon rats, all 

 led to the same conclusion. Two explanations appear to me to 

 account for the results, both of them involving the deterioration 

 of the egg. Either the gonads of old mothers produce eggs 

 in lower physiologic condition than younger mothers, or the eggs 

 are of the same or similar physiologic condition at any age, but 

 the interval between maturation and fertilization is greater in 

 older mothers and hence the eggs in poorer physiologic condition 



