JVIEM. M, C. Z., IX. No. 3. — ACALEPHS, POLYPS. tB 



14-37. PUurohrachia rliododactrijla. 



14. Embiyo of Pleurobrachia of about the same age, showing the relative position of the larger and smaller cells. 



15. A view of the same from the (oral ?) (actiual) axis. There is a confusion in dilfercut authors as to these 



two regions of the embryo. 



16. Older embryo of Pleurobrachia, showing the " actinal trench "(?) in prolile. ch. Epiblast. ga.^ Gastrie 



cavity, vt. cl. Vitelline masses. 



17. A schematic section, showing the relation between the cavity cja,^ the layer of sn)all cells c b, and the vitelline 



masses (i;<. c/.) bl p. Blastopore. 



18. Embryo o( Pleurobrachia, seen from the pole on which the blastopore {bl p) opens, cb. Outer layer of small 



cells. 



19. An embryo of the same, of about the same age as the last, seen from the ojiposite jiole. eb. Small cells. 



vt. cl. Large cells. 



20. Morula in which the small cells have almost completely enveloped the vitelline masses. 



21. An embryo showing the first elevation of eiriblastic cells to form an otocyst {ocy). cb. Epililast. 



vt. cl. Vitelline cells. 



22. Embryo older than the last, showing an infolding of the outer walls to form a stomach (ija). c b. Ejiiblast. 



c b. t. Prominence of the epiblast at the points where the tentacles later appear. 



23. An embryo of .about the same age as the last, seen from the actinal pole (o cy). 



24. Profile of the embrj'o in which the stomach cavity has formed. From A. Agassiz's account it seems that 



a part at least of the gastric cavity is hollowe<l out among the vitelline cells. This is the region of the 

 funnel or the upper part of the cavity {cja). 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 liypoblastic section, consisting of the infundibulum, and the gastro- 

 vascular canals derived from it ; and (2) an cpiblastic section — the stomodieum — forming the sto:nach. 



25. Older larva in which four otoliths (o/) have formed, cb. t. Tentacular prominence, t;. liow of vibratilc 



flappers. 



26. The same, a little older, seen from the actinal pole. ol. Otolitli. 



27. Still older embryo, e 6. <. Tentacular prominence. (/«. Stomach. o7. Otolith. 



28. Older larva. The otocyst is well formed, and the first of the two sections of the alimentary canal, mentioned 



above, has begun to have definite walls, ga. Stomach. 



29. View of a larva younger than tlie last, seen from the actinal pole. cb. t. Tentacular ]irondnence. ol. Otolith. 



30. An older larva with tentacles still more develojied. Otoliths {ol) brought close together into an otocyst 



(o cy). ta. Tentacle. 



31. Still older larva, seen from one side, in which the tentacles are well fomied. ga. Stomach, sph. Funnel. 



32. Older larva, girt. Stomach. spA. Funnel, te. Tentacle, tj. Row of locomotive flappers. 



33. View of a slightly older larva showing a tentacle on the middle line. or. Mouth, tj. Row of li;comotive 



flappers. 



34. More advanced embryo, or. Mouth. 77. Vibratile flappers. 



35. Side view of a larva a little older than the last. ga. Stomach. eg. Otocyst. 0!. Cluster of otoliths, to. 



Tent.acle. 



36. More mature embryo than the last (side view), ga. Stomach, or. Mouth, ta. Tentacle, rj. Vibratile 



flappers. 



37. The .same in another plane, ga. Stomach, or. Mouth. 



38-40. Calliaiiira bialata, Uelle t'hiaje, from Carl Chun, Fauna und Flora des Golfes von Neapel, I. Mono- 

 graphic : Ctenophorfo. PL 111. figs. 1, 2, 3. 



38. Larva before the formation of the lobes of the body on each side of the otocyst. 



39. Side view of the same or an older larva, ga. .Stomach. 



40. An older larva, with begiuiuugs of the vvingdike extensions of the body (w). /. tb. Lateral tube. ?;. Vibra- 



tile flapper. 



41-45. From Chun op. cit. PI. VIL fig. 18. PI. III. fig. 8. PI. VIll. fig. 8. PI. XIV'. figs. 9, 10. 



41. Larva of Cliiaja {Euchari.s) yjiuMicoriiis. hb. Hypoblast, tj. 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 tlie 

 future month. Rows of combs shoidd be represented at -q, and on the corresponding opposite side, while 

 a line indicating the lower edge of the mouth should connect the two prondnences at the lower pole. 



42. Embryo of iJeroe i^tirs/.-a/crt, Chun (optical section), c 6. Epiblast. /t6. Hyimblastie cells, nc. Munth. !t]ih. 



Lumen of the hypoblast. Tins cavity in the centre of the larva is the beginning of the future funnel. 

 T). Row of vibratile Haiijiei-s. eg. Otocyst. 



