SUMMARY OF CURRENT RESEARCHES. 501 



them to develop parthenogenetically. If tho sea-water contained only 

 a slightly greater proportion of K, we should find that Ghsetopterus 

 was " normally " parthenogenetic. 



A very striking fact is that the addition of a small amount of HC1 

 to the sea-water also induced the parthenogenetic development of the 

 Ohsetoptei-us eggs. 



Although the trochophore larvae which developed parthenogenetically 

 died in a day or two (as those originating from fertilised ova also did), 

 they were vigorous and normal ; but during the artificial parthenogenetic 

 development there is a stroDg tendency to amoeboid conditions and to 

 great indistinctness of cleavage. 



As in Arbacia, but more readily, giant embryos may arise by fusion 

 of two eggs, and dwarf embryos also occurred rarely in the experiments 

 with hydrochloric acid. 



Some strange facts are adduced which lead the experimenter to 

 surmise that the possibility of a successful hybridisation between 

 Echinoderm spermatozoa and Annelid ova is not to be dismissed as 

 ridiculous. But it will be time enough to consider such a crossing 

 when it is effected. 



A number of preliminary experiments were made on Phascolosoma , 

 Funclulus, Gonionemus, and Podarke. 



In general, Prof. Loeb believes that the spermatozoon can no longer 

 be considered as the cause or the stimulus of the process of development, 

 but merely as an agency which accelerates a process that is able to start 

 without it, only much more slowly. We may assume that the sperma- 

 tozoon carries a catalytic substance into the egg. Similarly, the K-ions 

 merely act as catalysers, accelerating a process which would otherwise 

 proceed too slowly. 



Parthenogenesis or Chemical Fertilisation* — Camille Viguier has 

 given a detailed account of his observations, in a paper which is in 

 great part devoted to a criticism of Loeb and to a response to his 

 criticisms. Viguier claims priority for the discovery that partheno- 

 genesis naturally occurs in Spliaerecliinus granulans, Arbacia pustulosa, 

 and Toxopneustes lividus, and he also records that he has been quite 

 unable to confirm Loeb's results. He furnishes an excellent biblio- 

 graphy. 



In another paper f Viguier reiterates his discovery of casual herma- 

 phroditism in Sph'derechinus granulans, and of casual but more frequent 

 parthenogenesis in the same species, in Toxopneustes lividus, and in 

 Arbacia pustulosa. 



Attending in particular to two risks — (1) of intra-ovarian fertilisa- 

 tion, and (2) of the entrance of spermatozoa in insufficiently filtered 

 water, Viguier made a fresh set of experiments. He convinced himself 

 of the occurrence of genuine parthenogenesis, in a few instances, in 

 Toxopneustes and Arbacia. But none got beyond the gastrula stage. 

 The author thinks that the relatively low temperature at the time of 

 experimentation had to do with this ; the development of fertilised ova 

 was much slower than usual. He suggests that the temperature may 



* Ann. Sci. Nat. (Zool.), xii (1900) pp. 87-138. , 

 t Couiptes Rendus, cxxxii. (1901) pp. 1436-8. 



Oct. 16th, 1901 2 m 



