278 , LEIGH HOADLEY. 



2. In contrast to the above, but showing the same general 

 order, are the concentrations of the same metallic salts which 

 are toxic to cleavage. These salts, with their toxic concentra- 

 tions are;— Au— N/7 5,825, Cu— iV/8,405, Al— N/445, Pt— 

 N/163.87, Ni— N/39 ~ . Cd— N/23 - , Co— N/6.5. There was so 

 much precipitation in the case of Zn, La, and Pb, that the 

 concentration of these salts, toxic to cleavage could not be 

 determined. 



Mercuric chloride proved toxic to cleavage at N/8 1,000, 

 while seeming to favor membrane elevation. At a concentra- 

 tion inhibiting membrane elevation, sperm were paralyzed 

 immediately. 



These concentrations vary slightly for different batches of 

 eggs and show the influence of a time factor, thus giving an 

 interesting contrast to membrane-inhibition, the concentrations 

 of which are more constant and immediate in their action. 

 These concentrations are greater in every case except Hg, than 

 the membrane-inhibiting concentration of the same metal. 

 Cleavage toxicity is a progressive, or a cumulative action. 



3. These solutions are not immediately harmful to the gam- 

 etes, but prolonged exposure is injurious to the eggs as can be 

 shown by two sets of experiments. 



(a) When the female gametes are exposed to the solutions for 

 various periods of time and are then inseminated in fresh sea- 

 water, the viability always stands in inverse ratio to the length 

 of exposure. 



(b) When the inseminated eggs are transferred to the solutions 

 at intervals after insemination in normal sea-water, the length 

 of exposure to the solution bears an inverse ratio to the viability 

 of the eggs. 



It will be seen in both (a) and (6) that the time factor is the 

 important one. The action here is again cumulative. 



4. With the exception of mercuric chloride, any harmful effect 

 of these solutions on the sperm is corrected by the addition of a 

 drop of egg sea-water. 



LITERATURE. 

 1. von Dungern, £. 



'02 Neue Versuche zur Physiologie der Befruchtung. Zeitschrift fur all- 

 gemeine Physiologie, Bd. I. 



