1904.] NATURAL SCIENCES OF PHILADELPHIA. 405 
of figures). Fig. 84 represents a section taken through a young 
veliger about the stage of that shown in fig. 104. 
Fig. 85.—Actual section through a gastrula similar in age to fig. 80 and in 
same plane. 
Fig. 86.—Actual section (sagittal) through a gastrula about the age shown 
in fig. 95. 
Fig. 87.—Actual section (about 30° to the right of the sagittal plane) 
through a young veliger slightly older than as shown in fig. 104. 
PLATE XXXII (except fig. 94), Figs. 88-89.—Actual sections (nearly horizon- 
tal) through a veliger about the stage shown in fig. 105, showing 
cerebral and pedal ganglia, pedal commissure and otocysts; also large 
excretory cell on right side of larva and large enteric cell on same 
side of enteron. 
Figs. 90-93.—Four successive horizontal actual sections through a veliger 
slightly older than that shown in fig. 107. 
Fig. 94.—Nearly horizontal actual section through veliger of same age as 
el series, showing nerve ring around cesophagus. On PI. 
XXXI. 
Pirate XXXIII, Fig. 95.—Gastrula, seen from right side, showing first indica- 
tion of the first velar row (V‘*). 
Figs. 96-97._Upper and lower sides respectively of gastrula of the same 
age as shown in fig. 95. 
Figs. 98-99.—Lateral (right) and lower sides of a veliger slightly older than 
that shown in figs. 96-97. 
Fig. 100.—Left side of gastrula somewhat older than that shown in the two 
preceding figures. 
Puate XXXIV, Figs. 101-102.—Anterior and right-lateral views of larva mid- 
way between gastral and veliger stages. The deep invagination of 
the shell-gland (Sh.G.) has formed and the stomodeal pit (St.) is 
well marked. 
Figs. 103-104.—Anterior and right-lateral views of a young veliger. The 
shell-gland has opened outward, the foot (Ft.) is becoming evident 
and the velar lobes are just beginning to appear. 
Fig. 105.—Veliger, seen from right side, somewhat older than the preceding 
one, showing further development of velar lobes and foot, developing 
shell, differentiation of enteron and larval musculature. 
Fig. 106.—Slightly older veliger than fig. 105, seen from right side. 
PuaTe XXXV, Figs. 107-108.—Dorsal and anterior views of the same veliger 
somewhat older than fig. 106. The shell and the velar lobes show 
considerable advance in development. 
Figs. 109-110.—Right-lateral and dorsal views of the same veliger just 
before hatching. The dotted lines represent the probable shape of 
the posterior vesicle before shrinkage. 
