6 U. 5. BUREAU OF FISHERIES, 
from eggs which are slow to cleave. It may be remarked that it is 
difficult to draw a strict line at times between the abnormal and the 
Fies. 18 to 22.—Sections of pike-perch eggs. Magnification, approximately xX 1620. 
Fic. 18a, 18b, 18c.—Side views of three sections of a plate showing 30 chromosomes, 
the normal number. , 
Fic. 19.—Side view of a plate in another cell in the same blastoderm as figure 11, 
sbowing 15 chromosomes, the haploid number, 
Fig. 20.—Polar view of normal plate. 
Fig. 21.—Abnormal multiplication of chromosomes. 
Fic. 22.—Abnormal elongated nucleus—abortive division. 
unsegmented types in the first few hours. At that time one or a few 
minute excrescences are occasionally budded from the germinal disk, 
