552 H. H. Newman 



determine some of the characters of the hybrids, such as the 

 maximum size on hatching, the rate of early cleavage, and the degree 

 of transparency of the embryo and of the yolk sac. It is scarcely 

 to be expected that a mass of protoplasm and yolk, such as the 

 fish egg, should show an immediate measurable alteration on the 

 entrance of a body comparatively so minute as the fish sperm cell. 

 It naturally takes time for the sperm cell to reorganize the com- 

 paratively enormous mass of egg protoplasm to such an extent 

 that the rate of the developmental process is measurably altered. 

 As a matter of fact it should cause some surprise that the sperm 

 cell is able to do this work in so short a time as it does. The 

 data cited above show that there was a distinctly measurable 

 retardation of the developmental process in the case of H 

 hybrids after a period as brief as fourteen hours, a time very short 

 as compared with the total period of embryonic development. It 

 is practically certain that this influence of the sperm cell was 

 operative at a much earlier period, even though it was not measur- 

 able by the crude methods applied. 



The only pure maternal characters that have been noted are 

 some of the characters that exist before the influence of the 

 sperm could reasonably be expected to make itself felt, and a few 

 mechanically determined characters such as have been mentioned. 

 In all other characters the sperm influence was evident in some 

 form or other. 



These results and conclusions are out of accord with the results 

 of Loeb^ and Godlewski,* who found that the larvae, produced by 

 fertilizing sea-urchin eggs with the sperm of holothurians and 

 crinoids, show d only sea-urchin (maternal) characters. 



It seems necessary to take exception to a statement made by 

 Conklin'-' in a paper that appeared since this work went to press, 

 "that the early development of animals is of purely maternal 

 type, and that it is only in stages later than the gastrula, and con- 

 sequently after the broad outlines of development and the general 



^ Loeb, J. University of California Publications, vol. i, 1904. 



* Godlewski, E. Arch. f. Entw.-Mech., 20, 1906. 



' Conklin, E. G. Science, vol. xxvii, no. 681, January, 1908. 



