THE EARLY DEVELOPMENT OF AMIA. 423 
nearly spherical, and the writer has observed that the blasto- 
pore of inverted eggs could slowly rotate downward. 
Deutoplasm and germ region are more early to be distin- 
guished in Amia than in other Ganoids. Studied in vertical 
sections (P1.31, fig. 21) the line of union of yolk and germ may 
be traced in the plane passing through the lower rim of the 
germ area; this plane of demarcation, however, on closer 
examination, proves to be broader than it at first appears; the 
yolk spherules may be traced, becoming smaller and smaller, 
well into the germ area. The nucleus, small in size, takes its 
position in the lower portion of the germ. 
“«‘ Pigment ” is practically absent in the late as well as in the 
earlier stages; in this regard the eggs of Amia and the gar- 
pike closely correspond. 
B. The Rate of Development.—The following summary 
of the rate of development relates to a particular set of embryos. 
It is evident, however, that the time-proportion between the 
different stages is relatively uniform for a longer or shorter 
period of development. The position with regard tothe upper 
and lower egg poles assumed by the growing embryos was 
observed by the writer to correspond with those he has already 
recorded in the Lepidosteus. Disturbance in the actual posi- 
tion of the egg, notably during the stages earlier than gastru- 
lation, is attended with variations of position; the lack of the 
power to rotate backward into its normal position has already 
been recorded, p. 422. 
Hours after oviposition. Hours after oviposition. 
Hours. Hours. 
First cleavage . : . 1 | Early gastrula . : AE, 
Second cleavage . 2 | Blastopore closes . 80 
Third cleavage . : . 3 | Embryo’s length 90°. 220/68 
Fourth cleavage . 4} a a SOR eid) 
Fifth cleavage . ae 7 pao . 124 
Sixth cleavage . ; . 6% ms Pao On. los 
Seventh cleavage ; . %% | Egg hatches . ; . 192 
The rate of hatching, as recorded by Filleborn, varied between 
eight to fourteen days. The present writer finds, however, that 
