39 2 OTTO GLASER. 



of the eggs, and rarely went beyond the blastula stage. As 

 stated before, I observed plutei only once, and not over ten or 

 twelve at that. Gastrulae also were rare. For this failure to 

 pass beyond the blastula stage there are several reasons; in the 

 first place one must attribute a large share to the fragmentation 

 of the early cleavage stages, due as I believe to the absence of a 

 normal fertilization membrane, and secondly the abnormal per- 

 meability relations resulting from the treatment with the secre- 

 tion probably also play a role ('i4 2 ) by placing mechanical dif- 

 ficulties in the way of gastrulation even though the necessary 

 materials are present in the embryo. The evidence for this 

 conclusion cannot be presented now. Although these obstacles 

 stand in the way of perfecting this method of rearing sea-urchins, 

 the fact that it is impractical, and inferior to other methods does 

 not in the least detract from the theoretical interest of the results. 

 As McClendon ('09) puts it : " In natural parthenogenetic develop- 

 ment the end result may be a maturation or segmentation stage 

 or a larva or adult. Though only the reproductive adults are of 

 significance to the species, all are of significance to science." 



AUTO-PARTHENOGENESIS IN Asterias. 



In earlier papers ('I3 1 , '14' and ! I4 2 ) I have emphasized certain 

 differences as well as certain points of similarity between the 

 eggs of Arbacia and Asterias. Chief among the differences, are 

 the characteristics of the fertilization membranes; most important 

 among the points of likeness are the decrease in volume to be 

 observed in both kinds of eggs on fertilization, and the fact that 

 . the Asterias ovum produces a secretion in which the most striking 

 characteristics of the corresponding Arbacia exudate can be 

 verified point for point. For these reasons one might anticipate 

 the initiation of development in the Asterias egg by the proper 

 employment of its own secretion. 



In the following experiments the secretion was prepared exactly 

 as in the case of Arbacia, but the eggs before treatment were given 

 time to mature, i. e., they were allowed to stand for about I hour 

 in sea-water after removal from the ovaries. 



10.27 A.M. i volume Asterias eggs. 10.27 A.M. 2 volumes Asterias eggs, 



i volume Asterias secre- i volume Asterias secre- 



tion, tion. 



