MORTALITY IN PIKE-PERCH EGGS IN HATCHERIES. 5 



abnormal. Eggs showing normal cleavage are shown in figures 2 and 

 3. Extreme variations, snch as are shown in figures 4 to 10, in 

 size of cleavage cells were found in nearly all cases to be correlated 

 with internal conditions which presaged embryonic death sooner or 



Figs. 11 to 17. — Sections of pike-perch eggs. Magnification, approximately X 200. 



Fig. 11. — Horizontal section of a normal egg of 64 or more colls. 

 Fig. 12. — From a 29-hour egg sliowing cj'ta.sters and abnormal .spindles. 

 Pig. 13. — From a 29-hour egg showing size variation in cytasters. 

 Fig. 14. — From an 8-hour 15-minute egg, showing elongated nucleus. 

 Fk;. 15. — From a 29-hour l."i-minute egg, showing partial segmentation. 

 Fk;. If — From a 29-hour 15-minute egg showing degeneration in chromatin and multi- 

 plication of chromosomes. 



Fig. 17. — From an 8-hour l;j-minute egg showing monaster. 



later. The number of such abnormal eggs increased steadily with 

 age, ranging from 1 per cent at 4 hours 30 minutes to 21 per cent 

 at 19 hours. As the curve in figure 1 shows, this increase runs 

 parallel with a decrease in the number of imsegmented eggs, which 

 suggests the possibility that such abnormal cases are derived chiefly 



