114 



Scientific Proceedings (34). 



ova is dependent upon and is an indicator of their combination 

 with the protoplasm of certain cells of the embryo. 



Now, it is not without interest to state that the toxicity of 

 neutral red varies according to the stage of development at which 

 the eggs are exposed to the influence of the staining solutions. 

 Ova immersed in a solution of neutral red and exposed to the light, 

 inside of sixteen hours after fertilization are most severely affected ; 

 ova exposed approximately twenty to thirty hours after fertilization 

 are somewhat more resistant, and ova which are exposed to the 

 light as late as two to four days after fertilization are affected only 

 to a very slight degree. 



Correspondingly, we find that the older the embryo becomes, 

 the less is it liable to be stained with neutral red and in embryos 

 five days old we usually find almost the whole embryo unstained 

 with the exception of the newly developed liver which appears in 

 an orange-yellow color. 



We may therefore conclude that the embryos of Fundulus 

 and their cells become less and less permeable for neutral red as 

 the development advances and that its toxicity decreases cor- 

 respondingly. 



A curve of toxicity almost parallel to that of neutral red we find 

 in the case of isotonic sodium chloride solutions. During the first 

 sixteen hours isotonic solutions of sodium chloride are extremely 

 toxic to the embryo of Fundulus ; from twenty to thirty hours there 

 is noticeable a certain decrease in toxicity ; while embryos two to 

 four days old develop in 5/8 N. sodium chloride solutions almost 

 as well as in sea water. We see, therefore, that the similarity of 

 the curves is very great and inasmuch as in the case of the neutral 

 red the variations in toxicity seem to depend upon variations in 

 the staining ability of this substance and therefore probably upon 

 the permeability of certain membranes or of the protoplasm of cer- 

 tain cells to the stain, we may assume as the most plausible ex- 

 planation that in the case of sodium chloride the variations in 

 toxicity also depend upon the permeability of certain organized 

 structures to the latter substance, and that therefore the conditions 

 of permeability in the embryo of Fundidus depend upon the same 

 conditions in the case of the lipoid soluble neutral red and in the 

 case of lipoid insoluble inorganic salts, a conclusion which is at. 



