402 H. H. NEWMAN 



eggs developed at least as far as the early cleavage stages: 82, 

 91, 77, 85, 72. There are always a few immature and possiblj^ 

 some overripe eggs and one gets about these same percentages 

 in a pure-bred lots of Fundulus eggs, so that we may conclude 

 that the percentage of fertility of Fundulus eggs with mackerel 

 sperm is about normal. 



Although the eggs in these experiments were well cared for and 

 casually examined from time to time, no detailed study was 

 made until nearly one week after fertilization, when the chromat- 

 tophores had made their appearance in abundance. On the 

 seventh day, however, a complete census of the hybrid embryos 

 was made on the basis of their relative success in development and 

 the heredity of maternal and paternal tj^es of chromatophores. 

 It was possible roughly to divide the entire lot into eight classes, 

 beginning with those that showed the most nearly normal devel- 

 opment and ending with those that had died since development 

 began. A full account of the conditions seen on the seventh day 

 is herewith given and is to be compared with another census 

 taken after nearly three weeks. 



Class A. A small group of three individuals apparently normal 

 in every way. The heart-beat is strong, the circulation abun- 

 dant and vigorous. .Although a little belated as to stage of devel- 

 opment as compared with pure-bred F. heteroclitus embryos of 

 equivalent age, they are exactly like the latter even in the 

 chromatophores which are pure maternal. It may be said that 

 from one to five such embryos appeared in all five experiments 

 and cannot be due to accidental insemination with F. heteroclitus 

 sperm. 



Class B. Five individuals are slightly retarded as compared 

 with class A, due evidently to their failure to establish a circula- 

 tion. The heart in each is large and pulsating vigorously, and 

 in two individuals contains some blood which moves back 

 and forth in the heart chambers as the pulsation drives it. The 

 chromatophores are all of the maternal type except that the black 

 chromatophores are somewhat more branching than one expects 

 in pure-bred Fundulus embryos. 



