130 Papers from the Marine Biological Laboratory at Tortugas. 



the size of the larvae. Driesch (1903) considered the same points, but by 

 the evidence neither was able to change essentially the belief of the other. 



About five years ago the controversy was given a somewhat different 

 form as a result of the researches of Loeb (1908) on heterogeneous hybrid- 

 ization. In this work an echinoid egg, Strongylocentrotus , was fertilized 

 by molluscan sperm, Chlorostoma, and the resulting plutei were taken as 

 evidence that the inheritance was purely maternal, i. e., from the egg alone. 

 The reason for this was shown by Kupelwieser (1909), who worked out the 

 cytology of the cross Echinus microtuherculatus female by Mytilus gallo- 

 provincialis male and was able to show that true fertilization did not take 

 place, the male nucleus never fusing with the female nucleus, but instead 

 lying at one side of the mitotic figure during division, the larvae resulting 

 from the cross being, in effect, parthenogenetic. 



Herbst (1906) obtained a closely similar result by a combination of 

 artificial parthenogenesis and fertilization, in which the larvae were held 

 to the maternal type. During segmentation the paternal nuclear material 

 lags and may fail to take part in the segmentation. Development in such 

 cases may be in reality maternal, but it is parthenogenetic. 



Results again resembling these were obtained by Giinther Hertwig 

 (19 1 2), when he inseminated sea-urchin eggs with spermatozoa which had 

 been subjected to radium rays and found that here again the male nucleus 

 failed to take a normal part in the processes of fertilization and cleavage. 



We must distinguish between the cases afforded by this work of Loeb, 

 Kupelwieser, and Hertwig, which deals in fact with a type of partheno- 

 genetic development, no fertilization taking place, and cases in which true 

 fertilization occurs, i. e., the union of an egg and sperm nucleus, although 

 here again we must distinguish between cases in which the union is only 

 temporary and those in which it is permanent. From work done by 

 Baltzer (1909, 1910), Herbst (1909, 1912), and Tennent (1912), evidence 

 has been gained which has proved that even though the two nuclei unite, 

 some of the chromosomes may be eliminated later. 



In Godlewski's (1906) fertilization of the echinoid egg with crinoid sperm 

 the union of the nuclei seems to have been permanent. In his fertilization 

 of enucleated fragments of sea-urchin eggs with crinoid sperm, the young 

 stages (gastrulae, four cases) were larvae which followed the sea-urchin type. 



Finally "partial fertilization," discussed by Boveri and Herbst, also rep- 

 resents a true fertilization, although the union between the nuclei may be 

 delayed until after segmentation has begun, and the resulting pluteus may 

 be in part maternal, in part hybrid in nature. 



The consideration of these points makes it clear that we have no estab- 

 lished evidence of the influence of the sperm on the characters of stages 

 younger than the pluteus and that new observations based on favorable 

 material is desirable. I count myself fortunate in obtaining material of 

 this nature while on the expedition made by the Department of Marine 

 Biology to Montego Bay, Jamaica. 



