THE PHYSIOLOGY OF CELL DIVISION 33 



Series I. Treatment with anesthetics after membrane-formation 

 by isotonic sodium chloride solution 



Brief exposure (five to ten minutes) to 0.55 m. NaCl is typically 

 followed by membrane-formation in a considerable proportion 

 of eggs, of which a minority develop to a larval stage. ^'^ This 

 mode of treatment is less favorable than exposure to acid-con- 

 taining sea-water or temporary warming, and even when a 

 favorable after-treatment is used the proportion of eggs reaching 

 larval stages rarely exceeds 20 or 30 per cent. Presumably the 

 initial cytolytic action of this solution is too energetic to be 

 readily counteracted or reversed by the subsequent anti-cytolytic 

 treatment. 



If eggs thus treated with salt solution are afterwards exposed 

 for half an hour to hypertonic sea-water or cyanide solution, or 

 sea-water containing anesthetics in appropriate concentrations, 

 the proportion of eggs forming blastulae is typically and often 

 markedly increased. The results of a series of such experiments 

 are summarized in table 1. 



In this series each form of after-treatment caused well-marked 

 increase in the proportion of eggs developing to a blastula stage. 

 It is to be noted that hypertonic sea-water was less effective than 

 the other solutions; this is very generally the case with starfish 

 eggs. After-treatment with hypertonic sea-water following mem- 

 brane-formation by salt-solution appears often to be more effec- 

 tive with eggs treated after the completion of maturation than 

 before. In three series where eggs from the same lots were thus 

 treated both (a) during maturation and (b) three hours after- 

 ward, the proportions forming larvae were : (a) < 1 per cent, (b) 

 20-25 per cent; (a) ca. 1 per cent; (b) ca, 20 per cent; (a) 1 per 

 cent; (b) ca. 10 per cent. No such differences were ever observed 

 with hypertonic sea-water used after the other two membrane- 

 forming agents. Cyanide and the anesthetics show well-marked 

 action in the above experiments. In the series shown in table 2 

 the effects of after-treatment with alcohols (ethyl, propyl, butyl, 

 and amyl) are illustrated. 



-•^ American Journal of Physiology, 1910, vol. 26, p. 119. 



THE JOURNAL OP EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 1 



