318 



SCIENCE 



[K. S. Vol. XL. No. 1026 



The writer had observed in his earlier ex- 

 periments on heterogeneous hybridization that 

 when 80 or 100 per cent, of the eggs of pur- 

 puraius formed membranes upon fertilization 

 with the sperm of starfish in hyperalkaline sea- 

 water, often less than one per cent, of the eggs 

 developed into larvse, while the rest behaved as 

 if only artificial membrane formation had been 

 induced. Last winter the writer and Dr. 

 Gelarie made sure that (as was already indi- 

 cated by observations of Dr. Elder) only those 

 eggs developed into larvae in which a sperm 

 nucleus was found, while the eggs which 

 formed membranes without developing did not 

 contain a sperm nucleus. The writer found, 

 also, that when the concentration of NaHO 

 and CaOl, used was comparatively high a 

 smaller proportion of the eggs with membranes 

 developed than when the concentration was 

 low. This was easily understood on the as- 

 sumption that the addition of NaHO as well 

 as of OaClj to the sea-water increased the ad- 

 hesion of the starfish sperm to the jelly of the 

 sea urchin egg, thus allowing the sperm to 

 induce membrane formation, but preventing 

 or rendering difficult its entrance into the egg. 



It occurred to the writer that if this as- 

 sumption was correct sea urchin eggs which 

 had been deprived of the surrounding jelly by 

 a treatment with hydrochloric acid should all 

 develop when fertilized with starfish sperm 

 and that they shoiild no longer show a mere 

 membrane formation without development. 

 This was found to be true. Sea urchin eggs 

 (purpuratus) were deprived of their jelly and 

 several hours or a day later fertilized with 

 starfish sperm in sea-water, to which some 

 CaClj and NaHO had been added. Often as 

 many as 50 per cent, of the eggs formed mem- 

 branes and practically all developed into 

 larvse; while the eggs of the same female not 

 deprived of jelly when fertilized under the 

 same conditions would all form membranes, 

 but with a very small percentage of eggs de- 

 veloping into larvse. This indicates that Ca 

 and NaHO may increase the adhesion of the 

 spermatozoa of the starfish to the egg jelly of 

 the sea urchin. It does not prove, however. 



that this increase of adhesive power is the 

 factor by which the CaCl, and NaHO influ- 

 ence the entrance of the spermatozoon into the 

 egg. It is possible that in addition these two 

 substances also influence the surface condi- 

 tion of the egg by increasing the fluidity of 

 the surface of the egg, thus favoring the 

 spreading of the fertilization cone of the egg 

 around the spermatozoa. 



5. The question arises whether or not the 

 addition of CaCl, and of bases favors the phe- 

 nomenon of sperm agglutination^ caused by 

 the supernatant sea-water of the eggs of the 

 same species, which ~F. Lillie has discovered. 

 This is not very probable, since the addition 

 of NaHO to sea-water shortens the duration 

 of the agglutination^ and therefore acts like 

 an " antiagglutinin." It is true that the addi- 

 tion of CaCl, favors the agglutination, but so 

 does the addition of MgCL; yet the latter sub- 

 stance without the presence of CaCh or the 

 addition of a base does not enable the sperma- 

 tozoon to enter the egg. 



It is, however, possible, if not probable, that 

 some specific substance in the surface of the 

 egg or spermatozoon or of both may also aid 

 in the entrance of the spermatozoon into an 

 egg of its own species. If this be true, in cer- 

 tain cases an excess of alkali or of CaCh may 

 compensate to some degree the lack of specific 

 siibstances for the entrance of the spermato- 

 zoon into the egg, e. g., in the fertilization of 

 the egg of the sea urchin by the sperm of star- 

 fish, brittle stars, holothurians and others. 



Jacques Loeb 

 The RocKErELLER Institute eok 

 Medical Eeseaech 



1 On the basis of observations on the sperm of 

 purpuratus the writer was doubtful whether the 

 specific cluster formation of the sperm caused by 

 the supernatant sea-water of the eggs of the same 

 species was a phenomenon of agglutination or a 

 tiopistie reaction. In Arhacia the agglutination 

 is much more pronounced than in the ease of 

 purpuratus. The surface tension phenomena 

 which the writer described may therefore find their 

 explanation on the assumption of an agglutination, 

 at least in the case of Ariacia. 



2 The Journal of Experimental Zoology, Vol. 17, 

 page 123, 1914. 



