482 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vou. VIII. 
Larva Ir mm. 
Each division of the anterior limb above noted is showing two tuber- 
cles, the four digits being thus indicated. he posterior limb has ex- 
changed its rounded contour for an angular one but no notches or grooves. 
appear on it. 
Larva 12mm. Figures to and 11. 
The digits of the posterior limbs appear as five tubercles, the second 
and the third of which are the most prominent. 
Larva 16mm. Figure 12. 
The posterior limbs are growing the more rapidly; they are now as. 
long as the anterior ones—2.5 mm.—and much stouter. Both pairs 
are provided with well developed toes. The gills have developed greatly 
each being two to three mm. long and consisting of a central stem with 
six or eight side branches. Considerable variation in the length of the 
gills is found in larve from different broods in what is otherwise the 
same stage of development, the shorter gills having also the shorter side 
branches. Some diminution of the yolk mass is for the first time notice- 
able, its vertical depth having lessened, though the attachment to the 
body is still along 3.5 mm. of the ventral surface. Sections show that 
in larvae from 9 mm. onwards the body walls are actually complete, 
but the more ventral part of the mesoblast is so much thinner than the 
dorsal and the line along which the two parts meet is so sharp as to pro- 
duce in the entire larva the appearance of having body walls developed 
only over the upper part of the yolk mass. At this stage rather more 
than the dorsal half of the yolk is covered by this thickened part of the 
body wall. The pigmentation typical of the adult is complete. 
Larva 17.5 mm. 
The posterior limb has outgrown the anterior, the lengths being 
3 mm. and 2.75 mm. respectively. ‘The length of the gills is reduced 
to 1.75 mm. or less. The yolk mass has so diminished as ‘to be almost 
covered in by the thicker parts of the body wall, only a portion 2.5 
mm. long and .5 mm. broad projecting slightly in the mid-ventral line. 
Larva 20 mm. to 25 mm. Figure 13. 
(just on the point of escaping from the mucous envelopes.) 
The anterior and posterior limbs are 3 mm. and 3.5 mm. long re- 
spectively. The yolk mass is almost entirely covered in. ‘The gills are 
