4.04 E. W. MACBRIDE. 
hydroceele. It shows also that the hydroccele has a wide opening into the 
anterior ccelom independent of the stone-canal. 
Fic. 47.—Sagittal section of a larva of Stage D, to show the relations of 
the lobes of the left hydroccele to each other. 
Fies. 48—50.—Three sections of a larva of Stage E. The larva has suffered 
an injury, a piece of ectoderm in the preoral lobe indicated by the dotted line 
being missing. Fig. 48 shows relation of rudiment of oral ccelom (or. c.) to 
the right dorsal horn of left posterior cceelom (/"p''e’.). Fig. 50 shows the 
great growth of the left hydroccele (compare Fig. 40). a. @. Adult cesophagus ; 
rudiment of the ‘‘stomach” of the adult. In Fig. 49 the o of ov.c. has failed 
to print. 
Fies. 51—53.—Three sections of a larva slightly older than the preceding, 
to show rudiments of the perihemal spaces (p/.). These are numbered ac- 
cording to the lobes of the hydroccele between which they occur: ph. 1.2, 
ph. 2.3, ph. 3.4, and ph. 4.5. ph. 1.2 arises from the anterior celom, the 
rest from the left posterior celom. The lobes of the hydroccele are com- 
mencing to be trifid. 
PLATE 21. 
The same remarks apply to this plate as to the two foregoing. 
Fics. 54—-57.—Four sections of a larva about midway between Stages E 
and F. Fig. 54 shows the incipient dorsal constriction of the anterior ccelom 
into a stalk portion (@.) and a body portion or axial sinus (a’.); also the origin 
of the perihemal rudiment (pA. 1.2) from the anterior celom. Fig. 55 shows 
the growing tip of the right ventral horn of the left posterior ccelom, and over 
it the arm rudiment No. V; it shows also the stone-canal opening into the 
hydroccele and the perihemal rudiment insinuating itself between the hydroccele 
and the ectoderm. Fig. 56 shows the axial sinus and the stalk ccelom con- 
tinuous with each other, and also the anterior ccelom opening into the right 
ventral horn of the left posterior cwlom. Fig. 57 shows that this right ventral 
horn is commencing to be again divided from the anterior ccelom ventrally 
by the outgrowth of a septum. 
Figs. 58 and 59.—Two sections of a larva slightly older than the preceding, 
to show the separation of the axial sinus ventrally on the one hand from the 
stalk ceelom, and on the other hand from the hydrocele. Py. Rudiment of 
the pyloric sac of adult. de. Last trace of the larval cesophagus. 
Fic. 60.—Section of larva about the same age as preceding, to show the 
fifth perihemal rudiment (p/. 51) which intervenes between lobes 5 and 1, 
as yet widely separated. 
Fie. 61.—Section of larva about Stage F, to show the mutual relations of 
the stone-canal, the axial sinus (a’.), the right dorsal horn of the left poste- 
rior ceelom (/"p"'c’.), and the right hydroceele (7Ay.). 
