AETIFICIAL PARTHENOGENESIS 487 



Briefly this may be stated as follows : With Ilyanassa, the errors 

 were fewest (per cent of error, 80), with Mytilus next, but with 

 a far greater number of errors (approximately 95 per cent) while 

 with Echinarachnius, although the cell-divisions progressed as 

 far as in Ilyanassa, yet the frequency of error was very large (only 

 a few developed in any one batch, but unfortunately the data in 

 percentages were not kept). No success was had with Phascol- 

 osoma. 



In the case of Arbacia, which differs in the manner of matura- 

 tion from Cerebratulus, the eggs maturing in the ovary, attempted 

 crosses with Mytilus and Modiolus were not successful, although 

 the experiments were given a great number of trials. The time 

 of applying the foreign sperm after the eggs were taken from the 

 ovary varied in the several cases, so that here again deference 

 was made to a possible 'refractory period.' 



The experiments outlined above are similar in many ways to 

 those which have been done by Steinbriick ('02), Loeb ('07, '09a), 

 Hagedoorn ('09), Godlewski ('05, '11), Kupelwieser ('09), Baltzer 

 ('10), Tennent ('10), and Bataillon ('09), where the eggs of a 

 number of echinoderms, mollusks, etc., were investigated with 

 a view to hybridization, with excellent results in several cases. 

 Some of these investigations pointed to the fact that even when 

 development proceeded after the addition of the foreign sperm, 

 nuclear fusion apparently did not take place, so that the action 

 of the sperm was that of giving an impetus to mitosis in the female 

 pronucleus, the male pronucleus disappearing, with the result 

 that larvae were maternal throughout. This was not true for 

 Baltzer's and Godlewski's experiments. Although cytological 

 material was preserved, the paucity of successes deterred me from 

 making sections of the eggs to determine whether th* results 

 were similar to those of the investigators named above and especi- 

 ally Godlewski, Baltzer and Kupelwieser, who made sections of 

 the eggs in various stages. 



While there is absolutely no question as to the results which 

 Kupelwieser, Godlewski and others obtained, it seems somewhat 

 strange that two species, Cerebratulus and Arbacia should respond 

 so slightly to the spermatozoa of other species, some of which 



