136 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 11. — Living and dead embryos per sample and their stage of development at 65° F. {12.8° C.) 



Table 12. — Mortalities of sea lamprey eggs reared at a 

 constant temperature of 55° F. (12.8° C.) 



[No sample on 24th day] 



I Terminal sample includes 11 live embryos mentioned in text as being 

 incapable of survival. 



Overlapping of stages was most limited with 

 the exception of stages 1 and 2 (overlap of 3 

 samples) and the last 2 (stages 13 and 14) (overlap 

 of 7 samples). Stage 13 was longest (127 hours 

 or about 5 days). Stage 8 lasted more than 54 

 hours and was also represented in 8 samples 

 (tables 6 and 13). Stage 14 was attained within 

 317 hours (about 13 days for first appearance). 



Percentages of dead embryos in samples rose 

 from a low of 32 percent during early cleavage 

 stages (1-6) to 88 percent in the terminal sample. 

 The rate of increase was highest in the early 

 stages actually during the first 2 days. Percentage 

 hatch (embryos that survived through stage 14) 

 though not accurately measurable from the 

 biased samples, obviously was good. 



The relatively few abnormalities during this 

 experiment (appro.ximately 20 percent) took 

 several forms, some of which were similar to 

 those described earlier. Among the more common 

 were enlargement of the pericardial area, and 

 the straight tubular heart which, nevertheless, 

 maintained a regular beat. Other specimens 

 exhibited abnormal curvatures, balloon mouths, 

 or cleft-lip. Abnormal curvatures of the trunk 

 region produced embryos with "C," "J," "O," 

 and "L" shapes. Balloon mouths were caused 



