158 H. H. Newman 



of the early development, including the polarity, symmetry, 

 type of cleavage, and the relative positions and proportions of 

 the future organs are predetermined in the cytoplasm of the egg. " 



Is it '' defitiitely settled that the early developniejjt of annuals is of 

 purely maternal type, and that it is only in stages later than the gas- 

 trula, and consequently after the broad outlines of development and 

 the general type of differentiation have been established, that the in- 

 fluence of the spermatozoon begins to make itself felt' ^? 



The experiments detailed in an earlier part of this paper show 

 that the spermatozoon exercises an hereditary influence upon the 

 rate of development at the earliest possible period when it could 

 be noticed or measured, and would seem to indicate that the 

 hereditary function of the male germ cell begins to operate imme- 

 diately, not after a period of abeyance. 



Godlewski has also shown in his hybrids that there is a well 

 marked retardation in the cleavage as early as the 4-cell stage. 



There is evidence also that the form of cleavage is subject 

 to the influence of the spermatozoon, as was indicated in Experi- 

 ment 6, where in the hybrid strain there was a preponderance of 

 irregular cleavages. This phenomenon is seen to much greater 

 advantage in another cross, produced by fertilizing the eggs of 

 Cyprinodon variegatus with the sperm of Fundulus heteroclitus. 

 In this case the whole cleavage is decidedly irregular after the 

 4-cell stage. 



Fischel' has shown that in a number of Echinoderm hybrids the 

 male influence is expressed structurally in the early blastula stages, 

 not only, in the general size of the embryos, but in the actual size 

 and shape of the cells. The sperm also seems to be responsible 

 for the production of a number of early monstrosities in which the 

 "broad outlines of development" have been decidedly distorted. 

 Such typical monstrosities are very common among Fundulus 

 hybrids and there is no doubt that similar conditions are found in 

 all hybrid experiments. 



Another phenomenon that has caught the attention of many 

 observers is the wide range of variability among hybrids. This 



'' Archiv. f , Entw. Mech., vol. 22, pp. 498-525. 



