SEX-CELLS OF AMIA AND LEPIDOSTEUS 7 
The number of sex-cells which have migrated from the ento- 
derm is found to be 674. It can be fairly taken as the number 
destined to undergo migration from the entoderm in this par- 
ticular individual. Those still remaining in the entoderm num- 
ber 133. | 
A few scattered sex-cells are found as far forward as the cranial 
end of the hind gut. The latter is 3.41 mm. in length. Opposite 
to the cranial portion of the hind gut the sex-cells are rather 
sparse, Increasing in number as one follows the series caudally. 
They become most numerous a short distance caudal to a point 
two-thirds the distance from the cranial to the caudal end of the 
hind gut. The last one in the mesoderm is found at a distance 
of .46 mm. from the cloaca, and the last one in the entoderm 
lies at a point .27 mm. from the cloaca. 
Lepidosteus 12 mm. total length. At this period migration of 
the sex-cells has progressed to the point where most of them have 
reached their final positions. They are still to be seen in the 
entoderm. This number (125) is quite close to that (133) of 
the similarly situated sex-cells of the preceding stage. The 
density of the mesodermal tissues surrounding the gut entoderm 
makes it seem quite unlikely that any more sex-cells could mi- 
grate into them from this source. 
The distribution of the sex-cells is as follows: 
Gut entoderm..... thes Ce, ore a oe 125 
Mesoderm of intestinal wall and 
INES emt Cryer eras cen cha ale ss 104 > 392 outside of sex-gland anlagen. 
Root of mesentery between sex- 
gland! Janlagemn.yoss.b a oaemer 3 os os 163 
iG SOKO LANG 2. ke so cure Ps whe ele » oe 180 
eee 
felt sex-gland... +s. sc. 0... 179 f 359 in sex-gland anlagen. 
The table may be allowed to speak for itself. The sex-gland 
anlagen grade into one another by an intermediate region at 
the root of the mesentery. More or less arbitrary limits had to 
be assumed to distinguish between these three regions. In 
later stages, illustrated by the 17 mm. stage, fig. 11, we shall see 
