XVI 



ANALYSIS OF THE ORIGINAL METHOD OF PRODUCING 



ARTIFICIAL PARTHENOGENESIS BY HYPERTONIC 



SOLUTIONS ALONE 



1. We are now able to undertake the analysis of the purely 

 osmotic method of artificial parthenogenesis by which the 

 writer first obtained parthenogenetic larvae of the sea-urchin 

 (see chapter vii). The reader will notice that this method ap- 

 parently contradicts the statement that artificial partheno- 

 genesis is due to the influences of two agencies, one of which 

 causes the membrane formation, the second the correcting 

 effect, which protects the egg against the disintegration in- 

 duced by the artificial membrane formation. The apparent 

 contradiction is abolished by the realization of the fact that 

 in this method the hypertonic solution acts simultaneously in 

 two capacities: first, as a cytoljdac agency causing a change 

 in the cortical layer (the formation of a gelatinous film), and 

 second, as a corrective agency. This latter effect is sufficiently 

 inteUigible from what has been said before. The cytolytic 

 effect of a hypertonic solution, however, needs to be demon- 

 strated, and, moreover, proof must be furnished that the two 

 agencies active in artificial parthenogenesis may act simultane- 

 ously instead of in succession. 



It must first be stated that this method also leads.to a kind 

 of stimted membrane formation; only such eggs can be caused 

 to develop by this method which form a membrane. 



But the hypertonic solution is not a rehable agency for the 

 causation of membrane formation, and this is the reason that 

 this original, purely osmotic method of artificial parthenogenesis 

 gives such poor results with the eggs of S. purpuratus and 

 not very good results with the eggs of Arbacia. The direct 



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