EFFECTS OF AGING UPON GERM CELLS. 23 



2. Such fusion may occur in the egg stage or during sub- 

 sequent development, with corresponding complete or incom- 

 plete fusion. The degree of fusion determined the various types 

 of fused embryos and larvae described in previous publications. 



3. Complete spontaneous fusion of not more than three eggs 

 occurred not infrequently and gave rise to giant eggs. 



4. Fusion occurred in all experiments in which the eggs were 

 allowed to age sufficiently. 



5. The variation in the time of fusion was determined by the 

 physiologic condition of the eggs at liberation. The more deterio- 

 rated the sooner the fusion. 



6. Fused eggs and embryos, and giant eggs occurred in all 

 three species of sea-urchin eggs, namely, Arbacia, Hipponoe and 

 Toxopneustes. 



7. It is probable that the "spontaneous" fusions of larvae and 

 embryos, described by many workers, find their explanation in 

 similar aging or deterioration of the eggs. 



C. I. With increasing age and physiologic deterioration of 

 the eggs, cleavage was increasingly irregular. This irregularity 

 was manifested in a change in size and shape of the blastomeres, 

 in retardation in the rate of cleavage, in increasing inhibition at 

 progressively earlier stages of development, increasing numbers 

 and types of atypic embryos and larvae, and in extreme stages, 

 in total lack of cleavage. 



2. In every batch of eggs irregular cleavage occurred as soon 

 as the eggs had aged sufficiently. The onset and the degree of 

 irregularity varied with the physiologic condition of the eggs 

 when liberated. Once begun there was a progressive increase in 

 the numbers and in the degree of abnormality. 



3. Irregular cleavage which is a consequence of aging is due 

 in part to excessive intake of sea water, and in part to poly- 

 spermy. The quantitative relations of these two factors was not 

 determined. Both are due to a change in the cortical layer of the 



egg- 



4. Deteriorated or irregularly cleaving eggs, were shorter 

 lived than physiologically fresh eggs. The greater the irregu- 

 larity (or physiologic age) the short lived the eggs, and vice 

 versa, the more virile the egg the greater the longevity and the 

 less irregular development. 



