268 LEIGH HOADLEY. 



even at this concentration so that the amount of the salt really 

 in solution could not be figured. Sperm will agglutinate readily 

 in such a solution, though the eggs become clumped. 



8. Nickel Chloride. — A series of tests, made with NiCl 2 , follow 

 so closely the general behavior of the metallic salts already 

 described that but little discussion is necessary here. It was 

 found the membrane inhibition first becomes evident at about 

 i : 30,000 when the percentage of membranes raised fell from 

 100 per cent, to 80 per cent, in immediate inseminations, while 

 at 1 : 5,000, iV/324, membrane elevation is completely supressed. 

 Such a solution, when used in a viability test, shows a decided 

 effect on the production of cleavages other than the first. The 

 effect is shown not only by the percentage of cleavage, but also 

 in its regularity. 



When tests were made to establish cleavage-toxicity, the 

 concentration required was found to be I : 600 or iV/39 — . Agglu- 

 tination of the sperm is good in I : 5,000 NiCl 2 when one drop 

 of the egg sea-water is added to 7.5 c.c. of thick sperm suspension 

 made up in the membrane-inhibiting concentration. The sperm 

 are active in such a solution even before the addition of the 

 egg sea- water. 



9. Cadmium Chloride. — Cadmium differs from the other metals 

 studied in only one respect and there the difference is quantitative 

 and not qualitative. When eggs are placed in the membrane- 

 inhibiting concentration, which is I : 1,333 + oriV/122.1, and after 

 various exposure times, are transferred to normal sea-water and 

 inseminated, there is a very marked poison effect after two 

 minutes exposure. Not only does two minutes exposure cause 

 very irregular development, even at the first cleavage, but it 

 tends to inhibit the elevation of membranes. After four 

 minutes, there were 98 per cent, membranes formed and 12 per 

 cent, were narrow. After one hour, all were narrow. When 

 eggs were exposed to the solution for one hour and then insemi- 

 ated, the first cleavage gave 16 per cent, regular forms and 42 

 per cent, irregular. 



The effect of this concentration on the sperm is very marked. 

 They agglutinate readily with egg sea-water and can be activated 

 by one drop of iV/500 NaOH or egg sea-water though they are 



