A NOTE ON THE SUSCEPTIBILITY OF SEGMENT- 

 ING ARBACIA AND ASTERIAS EGGS 

 TO CYANIDES. 1 



A. P. MATHEWS. 



The discovery by Lyon 2 that after fertilization sea-urchin eggs 

 show definite periods of resistance and susceptibility to the action 

 of cyanides is of such general interest that it is important to 

 establish the exact period at which eggs are most sensitive and 

 to discover whether other eggs also show similar periods of 

 susceptibility. Lyon found that the eggs were most easily killed 

 about the time of the first cleavage. He was in doubt as to the 

 exact period, but thought it came just after the cleav.age, whereas 

 immediately preceding cleavage the egg was very immune. He 

 made no sections and was not entirely certain with just what 

 processes in the egg these periods of immunity and susceptibility 

 coincided. Spaulding 3 tried similar experiments using ether and 

 acids. The ether especially gave a very sharp result and showed 

 great susceptibility immediately preceding segmentation. The 

 acid, as might be anticipated from the various actions it pos- 

 sesses, gave a far more complicated series of phenomena. It 

 seemed desirable to ascertain exactly the period of susceptibility 

 to the cyanides and to discover if possible what series of changes 

 within the egg corresponded with the periods of susceptibility and 

 immunity. A study was accordingly made of the living eggs of 

 Arbacia and Asterias and I have reexamined a series of sections 

 of Arbacia eggs made several years ago, in which the eggs were 

 preserved in sublimate-acetic at definite intervals after fertilization. 

 I also endeavored to repeat Lyon's observations on Arbacia using 

 Asterias Forbesii (?) eggs. Some very fine material was gathered 

 about the middle of September at Woods Holl. 



1 Laboratory of Biochemistry, University of Chicago, and the Marine Biological 

 Laboratory, Woods Hoi!. 



2 Lyon, American Journal of Physiology, VII., 1902, p. 56; XL, 1903, p. 52. 



3 Spaulding, BIOLOGICAL BULLETIN, VI. , 1904, p. 224. 



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