36. 
37. 
MEM. M. C. Z., IX. No. 3.—ACALEPHS, POLYPS. 33 
14-37. Plewrobrachia rhododactyla. 
. Embryo of Plewrobrachia of about the same age, showing the relative position of the larger and smaller cells. 
. A view of the same from the (oral 2) (actinal) axis. There is a confusion in different authors as to these 
two regions of the embryo. 
. Older embryo of Pleurobrachia, showing the ‘actinal trench” (?) in profile. eb. Epiblast. ga.! Gastric 
cavity. vf. cl. Vitelline masses. 
. A schematic section, showing the relation between the cavity ga,1 the layer of small cells eb, and the vitelline 
masses (vf. c/.) 61 p. Blastopore. 
. Embryo of Pleurobrachia, seen from the pole on which the blastopore (7p) opens. eb. Outer layer of small 
cells. 
. An embryo of the same, of about the same age as the last, seen from the opposite pole. eb. Small cells. 
vt. cl. Large cells. 
. Morula in which the small cells have almost completely enveloped the vitelline masses. 
An embryo showing the first elevation of epiblastic cells to form an otoeyst (ocy). eb. Epiblast. 
vt. cl. Vitelline cells. 
. Embryo older than the last, showing an infolding of the outer walls to form a stomach (ya). ¢6. Epiblast. 
eb. t. Prominence of the epiblast at the points where the tentacles later appear. 
. An embryo of about the same age as the last, seen from the actinal pole (0 cy). 
. Profile of the embryo in which the stomach cavity has formed. From A. Agassiz’s account it seems that 
a part at least of the gastric cavity is hollowed out among the vitelline cells. This is the region of the 
funnel or the upper part of the cavity (gz). The lower portion or the true stomach is formed as a gastrular 
invagination of the epiblast. As interpreted by Balfour, the alimentary canal of the Ctenophore would 
be made up of two sections : (1) a true hypoblastic section, consisting of the infundibulum, and the gastro- 
vascular canals derived from it ; and (2) an epiblastic section — the stomodieum — forming the stomach. 
. Older larva in which four otoliths (07) have formed. cb. ¢. Tentacular prominence. 7. Row of vibratile 
flappers. 
. The same, a little older, seen from the actinal pole, ol. Otolith. 
. Still older embryo. eb. ¢. Tentacular prominence. ga. Stomach. o/. Otolith. 
. Older larva. The otocyst is well formed, and the first of the two seetions of the alimentary canal, mentioned 
above, has begun to have definite walls. ga. Stomach. 
. View of a larva younger than the last, seen from the actinal pole. eb. ¢. Tentacular prominence. 07. Otolith. 
. An older larya with tentacles still more developed. Otoliths (0/) brought close together into an otocyst 
(ocy). ta. Tentacle. 
. Still older larva, seen from one side, in which the tentacles are well formed. ga. Stomach. sph. Funnel. 
. Olderlarva. ga. Stomach. sph. Funnel. ta. Tentacle. 4. Row of locomotive flappers. 
View of a slightly older larva showing a tentacle on the middle line. ov. Mouth. 7. Row of locomotive 
flappers. 
. More advanced embryo. or. Mouth. 7. Vibratile flappers. 
. Side view of a larva a little older than the last. ga. Stomach. ocy. Otocyst. o/. Cluster of otoliths. ta. 
Tentacle. 
More mature embryo than the last (side view). ga. Stomach. or. Mouth. ¢a. Tentacle. 7. Vibratile 
flappers. 
The same in another plane. ga. Stomach. or. Mouth. 
38-40. Cullianira bialata, Delle Chiaje, from Carl Chun, Fauna und Flora des Golfes von Neapel, I. Mono- 
38. 
39. 
40. 
41. 
graphie ; Ctenophore. PI. III. figs. 1, 2, 3. 
Larva before the formation of the lobes of the body on each side of the otocyst. 
Side view of the same or an older larva. ga. Stomach. 
An older larva, with beginnings of the wing-like extensions of the body (w). J. tb. Lateral tube. 7. Vibra- 
tile flapper. 
41-45. From Chun op. cit. Pl. VII. fig. 18. Pl. IIL. fig. 8. Pl. VIII. fig. 8. Pl. XIV*. figs. 9, 10. 
Larva of Chiaja (Bucharis) multicornis. hb. Wypoblast. 7». Position of the vibratile flappers. The thin 
layer which embraces the whole embryo is the epiblast, and the infolded region at the lower pole is the 
future mouth. Rows of combs should be represented at 7, and on the corresponding opposite side, while 
a line indie: 
ating the lower edge of the mouth should connect the two prominences at the lower pole. 
2. Embryo of Beroé Forskalea, Chun (optical section). ¢b. Epiblast. hb. Hypoblastic cells. or. Mouth. sph. 
Lumen of the hypoblast. This cavity in the centre of the larva is the beginning of the future funnel. 
n. Row of vibratile flappers. 0 cy. Otocyst. 
