THE DEVELOPMENT OF ASTERINA GIBBOSA. 407 
cele rudiment on the right side, with a distinct opening into ccelom: 
The left hydroccele is feebly developed for the stage which the larva 
has reached, and has only four lobes. 
Fig. 89. Section of a larva of Stage D, in which the right hydroccele has 
five lobes, and is larger than the left. This section is drawn from the 
ventral aspect, and hence appears reversed. 
Fig. 90. Section of a larva of Stage G, showing a “collar pore’ opening 
from the left hydroccele between lobes 2 and 3, directly to the exterior. 
Figs. 91—94. Four sections of an almost normal larva of Stage F, or 
somewhat older. p.c. Normal pore-canal, opening into axial sinus, 
the septum between the latter and the left posterior ccelom being 
still incomplete dorsally. p’.c’. Pore-canal, s¢’. c’., and stone-canal in 
connection with the right hydrocele. Fig. 93 shows the opening of 
the second pore-canal into the axial sinus. Fig. 92 ought to show 
the opening of the second stone-canal into the right hydroceele, but 
the slit-like opening has not come out in the figure. Fig. 91 shows the 
two pore-cauals uniting to open bya common pore. (Compare Wood- 
cut 3.) 
Fig. 95.—Section parallel to the larval plane from larva of Stage C, showing 
the first trace of right hydroccele. (Compare Plate 19, fig. 35.) Note its 
relationship to the anterior ceelom, which extends obliquely beyond it pos- 
teriorly, passing under it and to the right of it. Magnification 1000 diameters ; 
Leitz’s immersion 5. 
Fies. 96 and 97.—Two sections of body-wall of young star-fish, cut per- 
pendicular to disc, in which R equals ‘8 millimetre. Fig. 97 shows first trace 
of “ papula” or dermal branchia (4ranch.). Fig. 96, origin of its peribranchial 
space, p.dr. Magnification 400 diameters. 
Fic. 98.—Section of body-wall of young star-fish, in which R equals 
‘88 millimetre, showing dermal branchia and its peribranchial space. Mag- 
nification about 400 diameters. 
9 
PLATE 24. 
Fries. 99—106 illustrate the development of the so-called heart or “ ovoid 
gland.” The sections represented are perpendicular, or nearly so, to the 
disc of the star-fish, and the magnification is 850 diameters. 
Fig. 99. Section of larva of Stage G. ov.g. Fold projecting into the 
axial sinus, the rudiment of the ovoid gland. pr. germ. inv. Invagina- 
tion of peritoneum, whence the primitive germ cells are formed. Cue. 
Calcigenous tissue in the body wall. 
Figs. 100—108. Four sections of a specimen older than preceding. Fig, 
101 shows the growth of the primitive germ cells into the rudiment 
of the ovoid gland. Figs. 102 and 103 show that they do not yet 
extend through its whole extent. Fig. 103 shows that the ovoid gland 
