ARTIFICIAL PARTHENOGENESIS 491 



having been used in successful cases (Mytilus).'^ I have repeated 

 Kupelwieser's experiments in a manner as nearly like his own as 

 I could, judging from the printed account without any suggestion 

 of the success, as far as echinoderm-mollusk crossing is concerned, 

 which he experienced, but terminating without the production 

 of later stages than morulas, even when artificial parthenogenetic 

 media were applied. 



With the exception of Ilyanassa, whose eggs were not ripe at 

 the time the experiments were performed at Harpswell, checks were 

 employed to insure that the spermatozoa of the foreign species 

 were functional and normally so. However, in the case of Ilya- 

 nassa, the spermatozoa were highly active under the microscope 

 and there is little reason to doubt that they were functional. 



There are many other species of invertebrates which show a 

 decided obstinacy to both artificial parthenogenetic reagents and 

 to crossing, although failures are seldom reported, which leads to 

 difficulties for other investigators. Prof. E. G. Conklin of Prince- 

 ton University and Dr. J. F. McClendon of Cornell University 

 Medical College have testified to me personally that they have 

 tried several forms which did not respond in any way to artificial 

 reagents. Thus, ascidians seem to be in this category and like- 

 wise some of the mollusks, Mytilus eggs having been given a good 

 test by McClendon with no success. If the roster of such forms 

 be made from the experience of investigators, I have httle doubt 

 that a large number of such species will appear. It seems to me, 

 therefore, that there is a problem involved which should attract 

 attention and be attacked from several points of view — cytologi- 

 cally, physical-chemically, chemically and from the standpoint 

 of environmental differences. I have attempted to follow out 

 a few of these lines, with the success noted in the paragraphs above. 

 Until w^e are able to explain, at least in a way, why several eggs 

 are not amenable to the same reagents and methods that a great 

 variety of others are, our conception of fertilization and of the 

 role of the spermatozoon cannot be final. It is only by the record 

 of failures and successes that any advance in the knowledge of the 

 matter in question will be made; the method of trial and error is 



8 Tennent ('10) found that Toxopneustes X Holothuria went only to segmenta- 

 tion. 



