538 H. H. N 



ewman 



dition of [Hi) while the germ band of /f pures was on the average 

 more than halfway around the yolk. At 43 hours the blastopore 

 in H pures was nearly closed, more advanced than (m^), while in 

 H hybrid the germ band was less than one-half way around the 

 yolk and the embryo was very ill defined, between {Hz) and (mj), 

 nearer the former. At 89 hours H pures resembled (m^); H 

 hybrid {m^)\ M hybrid (mj); and M pures {m6). 



Series D, July 2, igo6. This series was reared to hatch and was 

 observed only incidentally while the water was changed from 

 time to time. Just before hatching, however, counts of heart 

 rates were made with the following results: 



H pure — 100, 108, 108, 106, 96, no, 112, 120, 106, no. 



Average 107.6. 

 i^ hybrid — 100, 130, 148, 120, 116, 100, 130, 120, 122, 124. 



Average 121. 

 M hybrid — 74, no, 82, 96, no, 116, 56, 100, 96, 90. 



Average 93. 

 M pure — 112, 120, 124, no, 126, 120, 120, no, 128, 126. 



Average 119.6. 



In this series the heart rate of the two hybrids were the extremes 

 while the two pure breeds occupied a mean position. 



Series E, July ii, igo6. This incomplete series was strikingly 

 in accord with Series i as far as it went, but was not followed after 

 42 hours, at which time drawings of typical specimens of all four 

 strains were made, H pure resembling (/z^), H hybrid resembling 

 {m/f) with blastopore almost closed, M hybrid resembled {Hz), 

 and M pure resembled {hz). 



Series F, June 2^, J^poy- This series was followed carefully 

 for four days when it had to be abandoned, on account of 

 absence from the laboratory. At 48 hours this series showed the 

 unusual character of having the M pures decidedly in advance of 

 the M hybrids. At the end of three days, however, the M hybrid 

 had forged distinctly ahead. 



Series G, July 8, igoy. No observations recorded except at 

 time of hatching. H pures had all hatched at the end of fifteen 

 days while none of the H hybrids had hatched. Two days later 

 the majority of the latter had hatched. 



