1899] PARTHENOGENESIS IN A SEA-URCHIN 383 
sea-water* 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 
egos. 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 végétale de Meudon” from 
1883 to 1899 (“Chimie végétale 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. 
