480 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
Though thus hidden from view by the beginning of the tail, sections 
show the blastopore opening into the bottom of this furrow. At this 
time the increase of fluid around the egg begins. The whole body is as- 
suming a cylindrical form and standing out from the yolk which is slightly 
flattened near it, and markedly flattened in the region against which 
lies that part of the body from the anterior limbs forward. 
Larva6mm. Figure 7. 
During the growth from 5.5 mm. a twisting of the anterior part of 
the body through 90 degrees has occurred so that one side of the head 
is now turned toward the yolk; of eleven specimens this was the right 
side in nine, the left side in two. That portion of the body attached to 
the yolk, 7.e., all posterior to the pharyngeal region, shares in the twisting 
and becomes curved laterally upon the yolk in such a fashion that the 
anterior three-fourths of the dorsal surface is brought into the one plane. 
Opposite and external to the last three somites now distinguishable is, 
on each side of the body, a low mound of thickened tissue—the begin- 
nings of the posterior limbs. The terminal millimetre of the tail is quite 
cylindrical and free from the yolk. The first traces of pigmentation 
now appear on the dorsal surface of the anterior part of the body. 
Larvagmm. Figure 8. 
The anterior part of the body has more than doubled in thickness and 
has grown so far off the yolk that the anterior limbs are now free from 
contact with it. This gradual freeing of the body from its attachment 
to the yolk is brought about by growth of the central part of the body 
crowding off the extremities, accompanied by but little pinching off of 
the connection between body and yolk; for the length of body attached 
to the yolk has remained, and will for some time yet remain, constant at 
3.5 to 4 mm. As the body is thus projected forward those parts of it 
that were spread out laterally on the yolk move ventrally and unite in 
the middle line. This is well shown in the anterior limbs which from pro- 
jecting dorsally as at first are compelled by this movement at last to 
point outwardly. They are now .35 mm. long. Similar growth back- 
ward has brought the posterior limbs to the verge of the attachment 
of body and yolk posteriorly. These limbs are yet represented by 
rounded thickenings only. All traces of the gill arches have disappeared 
from the surface while the external gills have appeared as three points 
.25 mm. in length. The costal grooves are visible and pigment in a broad 
band extends over the dorsal surface of the neck and anterior half of 
the trunk. sy 
