FOURTEEN TELEOSTEAN FISHES AT BEAUFORT, N. C. 
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size, is distinct from the smaller perch egg, as its range in size is about 0.8 to 0.88 
millimeter and its average is close to 0.84 millimeter. It seems probable, therefore, 
that this larger egg is from a different species. However, we have not yet succeeded 
in determining by which species it is produced. 
Segmentation and the development of the embryo . — Segmentation occurs very quickly 
after fertilization takes place. (Fig. 16.) Eggs held in glass sediment dishes at a 
temperature varying from 67° to 69° F. reached the 2-cell stage (figs. 17 and 18) 
within one-half hour after fertilization, the 4-cell stage (fig. 19) within three-fourths 
of an hour, and an advanced cleavage stage (fig. 21) within 6 hours. Twelve hours 
after fertilization the germ ring had become visible in many of the eggs, within 24 
hours the embryo was well formed (fig. 22), and at 36 hours the more advanced eggs 
Figure 16.— Orthopristis 
chrysopterus. Egg with 
fully developed blasto- 
dise, a few minutes after 
fertilization. Normal egg 
about 0.75 millimeters in 
diameter 
Figure 20. — Orthopristis 
chrysopterus. Egg in 8-cell 
stage, surface view, about 
one hour after fertilization 
Figure 17.— Orthopristis 
chrysopterus. Egg in 
2-cell stage, about a half 
hour after fertilization 
Figure 21. — Orthopristis 
chrysopterus. Egg in late 
cleavage stage, side view 
Figure 18.— Ortho pristis 
chrysopterus . Egg in 
2-cell stage, same as Figure 
17, surface view 
Figure 22. — Orthopristis 
chrysopterus. Egg em- 
bryo, showing distribu- 
tion of chromatophores, 
about 24 hours after fer- 
tilization 
Figure 19.— Orthopristis 
chrysopterus. Egg in 4-cell 
stage, surface view, about 
three-fourths of an hour 
after fertilization 
Figure 23.— Orthopristis 
chrysopterus . Embryo 
shortly before hatching, 
about 36 hours after fertili- 
zation. Heart action is evi- 
dent at this stage 
began to hatch (fig. 23). Early in the season the eggs developed less rapidly, but 
late in the season, when the temperatures were running high in the laboratory, de- 
velopment proceeded even more rapidly than described in the foregoing lines. It 
became very difficult, though, to hatch the eggs at the higher temperatures, as many 
of them died in various stages of development, apparently due to the excessive heat. 
The incubation period at the temperatures (ranging from about 60° to 85° F.) that 
prevail in the local waters during the spawning season, judging from results obtained 
in the laboratory, probably ranges from about 36 to 72 hours — the shorter period of 
time being required late in the season when temperatures are high and the longer 
period earlier when temperatures are low. 
