458 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



which induces membrane-formation without previous dilution, for the 

 concentration of proteins in normal undiluted serum is sufficient to 

 inhibit the membrane-formation succeeding fertilization by sperma- 

 tozoa. It is, however, possible to increase the "charge" of membrane- 

 forming agent in spermatozoa by sensitizing them with strontium 

 chloride solution and exposing them to blood-serum previous to fer- 

 tilization. They thus accumulate the membrane-forming agent from 

 the serum and carry it together with their own membrane-forming 

 agent into the egg. The following experiment affords an illustration 

 of this fact. Solutions of ovomucoid in sea-water were prepared con- 

 taining 2, J, J and f per cent, of the protein, respectively and in 

 2 c.c. samples of each of these solutions were placed two drops of a 

 thick suspension of the eggs of Strongylocentrotus purpuratus. The 

 sperm from a male of the same species was divided into three portions. 

 The one portion was untreated save by washing in sea- water. A second 

 portion was immersed for four minutes in f m. strontium chloride and 

 then for one minute in sea-water. The third portion was immersed 

 for four minutes in f m. strontium chloride and then for four minutes 

 in an isotonic undiluted blood serum. These three samples of sperm 

 were then added to the eggs contained in the solutions of ovomucoid 

 in sea-water described above. The concentrations of ovomucoid 

 employed inhibited the formation of fertilization-membranes by the 

 normal spermatozoa and by those which had merely been immersed 

 in strontium chloride solution, but, except in the case of the strongest 

 solution, they were unable to prevent the formation of membranes by 

 the spermatozoa which had acquired an additional charge of cytolytic 

 substance from blood serum : 



It appears, therefore, that the cytolytic agent in mammalian blood- 

 serum when introduced into the egg-cell together with the sperma- 

 tozoon, brings about just the same effects as the cytolytic agent in the 

 spermatozoon itself and the inference is thus rendered the more prob- 

 able that these two agents are similar in character. 



THE EFFECT OF MEMBRANE-FORMING AGENTS UPON THE EGG. 



The essential feature of the process of Membrane-formation is its 

 evidently close relationship to the phenomena of Cytolysis, or lique- 

 faction and disintegration of the cell. In the view of Loeb it is cytolysis 



