1899] PARTHENOGENESIS IN A SEA-URCHIN 383 



sea-water J was able to bring about the same effect as the entrance of 

 a spermatozoon. The unfertilised eggs [of the sea-urchin Arbacia] 

 were left in such a solution for about two hours. When brought back 

 into normal sea- water they began to segment and form blastulae, 

 gastrulae, and plutei, which were normal in every respect. The only 

 difference was that fewer eggs developed, and that their development 

 was slower than in the case of the normal development of fertilised 

 eggs. With each experiment a series of control experiments was made 

 to guard against the possible presence of spermatozoa in the sea-water." 

 Professor Loeb's conclusion is " that the unfertilised egg of the sea- 

 urchin contains all the essential elements for the production of a 

 perfect pluteus." " All the spermatozoon needs to carry into the egg 

 for the process of fertilisation are ions to supplement the lack of" 

 favourable ions, " or to counteract the effects of the other class of ions 

 in the sea-water, or both. The spermatozoon may, however, carry in 

 addition a number of enzymes or other material. The ions and not 

 the nucleins in the spermatozoon are essential to the process of fertilisa- 

 tion." Professor Loeb believes that the same principles hold good for 

 the fertilisation of other, if not all, marine animals, although the ions 

 involved will probably differ in various species. By marine animals he 

 seems to mean those whose eggs are deposited before fertilisation. At 

 all events he does not include mammals, in which class he considers it 

 possible that parthenogenesis is prevented only by the ions of the 

 blood, and that a transitory change in those might allow of it. 



The experiments and conclusions of Loeb are consistent with those 

 of Delage, Ziegler, Norman, Driesch, and others. All the ideas as to 

 the extreme importance of nucleus, and centrosome, and polar bodies 

 and the like, are being much shaken, and it seems as if the ground 

 were being cleared for an entirely new and far less complicated theory 

 of sexual reproduction and heredity. It would be interesting to com- 

 bine the experiments of Delage and Loeb, and to see if an ovum could 

 be made to develop without either its own nucleins or those of the 

 spermatozoon. 



The Record of a Great Work. 



In four thick volumes the famous chemist Berthelot has told the story 

 •of his work at the " Station de Chimie vegetale de Meudon " from 

 1883 to 1899 ("Chimie vegetale et agricole." Paris: Masson et Cie. 

 1899). The first volume deals with the experiments bearing upon the 

 fixation of nitrogen by micro-organisms in the soil or associated with 

 the roots of Leguminosae, by silent electrical discharges in the air, and 

 by other means. In the second volume the central subject is the 



1 These numbers are according to corrections made by the author in a reprint kindly- 

 sent by him. 



