THE PHYSIOLOGY OF CELL DIVISION 43 



pensation and hence in injury. Whether the after-treatment 

 is favorable or not thus depends on the physiological condition 

 of the egg. Its action is at best supplementary, and is superflu- 

 ous or injurious whenever the egg is capable of regaining the 

 normal condition unaided. 



As with the first series of anesthetics, it was found that treat- 

 ment with alcohols alone, without preliminary membrane-forma- 

 tion, leaves the great majority of eggs apparently unchanged. 

 A small and variable proportion of eggs so treated may, however, 

 fonn membranes and develop, as in the above experiments with 

 ether, urethane and chloretone. The essential physiological ac- 

 tion of the alcohols, like that of the other anesthetics, is thus 

 different from that of the membrane-forming agency, and proba- 

 bly consists in a modification of the membrane in the direction 

 of decreased permeability.- 



Series III. Treatment with anesthetics after membrane-formation 

 by temporary warming 



Brief exposure of starfish eggs during the maturation-period to 

 temperatures of 34° to 38° induces typical membrane-formation 

 followed by cleavage, which in favorable instances leads to the 

 production of a considerable proportion of larvae. As with the 

 other membrane-forming agents, this proportion may be in- 

 creased by after-treatment with hypertonic sea-water," cyanide, 

 or anesthetics. Table 8 gives a summary of four typical series 

 of experiments, in which urethane, chloretone, and ether show well- 

 marked favorable action, while chloral hydrate and cyanide are 

 less effective ; hypertonic sea-water again proves relatively ineffec- 

 tive as compared with the other solutions. Two series of exper- 

 iments with alcohols gave similar results, summarized in table 9. 



After-treatment with alcohols is thus highly effective with eggs 

 subjected to this type of membrane forming treatment. In these 

 experiments (table 9) propyl, butyl and amyl alcohols appear more 

 favorable than ethyl alcohol, and the same was very generally 

 observed in last summer's experiments with starfish eggs. In my 

 experiments with Arenicola larvae, propyl and butyl alcohols 



