CYTOLYSINS IN SNAKE VENOM 



203 



Table 15. — Continued. 



Flexner and Noguchi next determined the action of venom upon the fer- 

 tilized ova of Fundulus, Arbacia, and Asteria. Observations upon these cells 

 were conducted under two sets of conditions: (a) fertilization was attempted in 

 venom solutions, and {b) venom in solution was added to the fertilized eggs 

 at different periods of segmentation. The following facts appeared: 



Fundulus ova: 



(i) Venom in strong solution (5 per cent cobra) dissolves the fertilized ova, 

 but in weaker solution only delays segmentation. 



(2) After fertilization and beginning segmentation weak solutions of venom 



do not prevent further segmentation. 



(3) Brief treatment with weak venom solutions of the segmenting ova up to 



the time of the morula stage causes only delayed development. 



(4) Brief treatment of the embryos with weak solutions at about the period 



of formation of the brain and optic vesicles (36 hours) causes malforma- 

 tion and delays the hatching. 



(5) More advanced embryos are more resistant, but finally may succumb 



to venom poisoning. 



Arbacia and Asteria ova: 



(i) Strong solutions (5 per cent cobra) of venom prevent fertilization, but 

 weak solutions permit its occurrence. 



(2) Strong solutions of venom delay segmentation, while weak solutions 



cause imperfect and irregular segmentation. 



(3) Brief treatment with weak venom solution accelerates the blastula forma- 



tion, while the plutei are killed by strong solutions of venom. 



