1 8 A. J. GOLDFARB. 



All these apparently diverse methods have this in common, viz., 

 that they all induce the same changes in the eggs, i. e. accelerate the 

 aging of eggs, and thus permit the ready entrance of autogenous 

 or heterogenous sperm. Instead of emphasizing the one or the 

 other external agent or change, as Herbst has done, I prefer to 

 emphasize that which is common to all, namely, the very definite 

 morphologic and physiologic changes within the egg, which I 

 have termed physiologic deterioration or aging. 



There are on record other phenomena which may now be inter- 

 preted in terms of the known changes in aging eggs, and which 

 may be briefly summarized as follows : 



Vernon ('95, '98) observed a seasonal change in the size of the 

 larvae, in the per cent, of hybridization, in the per cent, reaching 

 the larval stage, in the maternal or paternal type of hybridized 

 larvae. These seasonal changes are in all probability due, as he 

 himself suggested, to the varying physiologic conditions of the 

 eggs, at different periods of the breeding season. 



Fuchs ('14) observed that the per cent, of self-fertilizations in 

 done increased with the age of the eggs. This is exactly what 

 one should expect from the known changes in aging eggs and of 

 the ready entrance of sperm in old eggs. 



Matthews ('01) could induce parthenogenesis by shaking 

 (in Asterias forbesii], most readily, when the eggs were at least 

 three hours old. 



De Vries, according to Vernon, obtained a larger per cent. (40) 

 of mutants in old seeds, whereas fresh seeds gave only I to 5 per 

 cent. This suggested that not only may the protoplasmic parts 

 of the egg be radically modified by aging, but that the nuclear 

 parts may be correspondingly affected. 



Other experiments serve to strengthen this conclusion, par- 

 ticularly those upon sex determination. 



R. Hertwig ('06 and '07) and Kuschekewitch were first to 

 note that sex could be altered by aging the eggs of the frog. 

 More recently Riddle ('i2-'i4), experimenting with pigeons, 

 concluded that the sex of the offspring was conditioned by the 

 physiologic activity of the reproductive organs or by the age of 

 the mother. Both hyperactivity and aging of the mother causes 

 an excess of male-producing eggs. 



