FURTHER STUDIES OF THE PROCESS OF HEREDITY 

 IN FUNDULUS HYBRIDS' 



H. H. NEWMAN 

 With Seven Text-Figvres 



I. THE INFLUENCE OF THE SPERMATOZOON ON THE RATE AND 

 CHARACTER OF EARLY CLEAVAGE 



In a previous paper on Fundulus hybrids- it was stated that 

 the developmental rhythm of the young embryo was distinctly 

 influenced by the foreign spermatozoon as early as fourteen 

 hours after fertilization. It was also conjectured that the influ- 

 ence ot the male cell was operative at a much earlier period, 

 although it did not manifest itself in a measurable degree. 

 Attempts were made to test the influence of the foreign sperm 

 upon the early cleavage rhythm, but the results were largely 

 negative owing to the crudeness of the methods employed. 



As the writer was convinced that these results needed reexam- 

 ination, the work was resumed during the summer of 1909. This 

 time the methods proved to be sufficiently refined to suit the case 

 and positive results were obtained. The treatment was statisti- 

 cal in the sense that very large numbers of eggs were examined, 

 and this involved an amount of tedious labor and eye-strain 

 probably out of proportion to the value of the results obtained. 



During the earlier attempts much difficulty was experienced in 

 obtaining satisfactory data concerning the rate of cleavage. It 

 seems a simple enough matter, to one who has not made the at- 

 tempt, to enumerate the 2- and 4-cell stages in a batch of a thou- 

 sand eggs or more. In realitv, however, the diflRculties are numer- 



' Contributions from the Zoological Laboratories, University of Texas, No. icxD. 

 ■' Journal of Experimental Zoology, vol. v, no. 4. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 8, NO. 2. 



