xviii INVERTEBRATA 



FIO. PACK 



30. Section of embryo of Tubularia mesembryanthemum showing the formation 



of the aboral tentacles ....... 56 



31. Five views of external features of different stages in the development of the 



embryo of Tubularia indivisa ...... 56 



32. Two gonophores of Tubularia indivisa with developing embryos inside . 57 



33. Stages in the development of the Actinula larva of Tubularia indivisa . 57 



34. Three longitudinal sections through the developing gonophore of Tubularia 



mesembryanthemum . . . . . . . .58 



35. Four transverse sections through the developing gonophore of Tubularia 



mesembryanthemum. . . . . . . .59 



36. Longitudinal section through very young gonophore -bud of Tubularia 



mesembryanthemum to show the origin of the genital cells . . 59 



37. Four stages in the development of the planula of Clytia . . .60 



38. Three stages in growth of the fixed planula of Clytia . . .60 



39. A young colony of Clytia reared from a planula in the aquarium . . 61 



40. Two longitudinal sections through the developing medusa of Podocoryne 



carnea ......... 62 



41. Four transverse sections through the developing medusa of Podocoryne 



carnea in order to show formation of circular canal and endoderm lamella 63 



42. Two longitudinal sections through the developing gonophore of Clava 



squamata ......... 64 



43. Three stages in the development of a Siphonoplibre (Cystalia monoyastrica) 65 



44. Embryo of a Geryonid (Car marina fungi for mis) in which endoderm cells 



are being budded off ....... 67 



45. Early stages in the development of Aurelia aurita . . . .68 



46. The fixation of the free-swimming larva of Aurelia aurita . . .68 



47. Two longitudinal sections through two Hydra-tubae of different ages . 69 



48. Two transverse sections through a Hydra-tuba with four tentacles . . 70 



49. A, a Hydra-tuba with eight tentacles. B, longitudinal section of a part of 



a similar specimen in order to show origin of septal funnels . . .71 



50. Oral view of Hydra-tuba with twenty tentacles. (The tentacles are repre- 



sented as cut off) ... . . . . . .71 



51. Two horizontal sections through the upper part of a Hydra-tuba, about as 



old as that represented in Fig. 50, to show the formation of the ostium 

 connecting the stomach pockets ...... 72 



52. Two stages in the strobilization of the Scyphistoma of Aurelia aurita . 73 



53. A strobilized Scyphistoma of Aurelia aurita . . . . .74 



54. An Ephyra larva of Aurelia aurita just after liberation from the strobiiized 



Scyphistoma ........ 74 



55. Longitudinal section through the sense organ of a young Ephyra . . 75 



56. Three stages in the development of the Ephyra larva into the adult Aurelia 75 



57. An egg of Urticina crassicornis dividing into sixteen blastomeres . . 77 



58. Four stages in the development of the egg of Urticina crassicornis as seen 



in longitudinal sections ....... 78 



59. Two stages in the development of the larva of Urticina crassicornis . 79 



60. Two transverse sections through a larva of Urticina crassicornis in order 



to show the formation of mesenteries ..... 80 



61. Transverse section through a larva of Urticina crassicornis in which the 



tentacles have just been developed ...... 81 



62. Longitudinal section through the larva of Agaricia agaricites in order to 



show the ectodermal origin of the mesenterial filament . . .82 



63. Stages in the development of the larva of Actinia equina . . .84 



64. The Arachnactis larva of Cereanthus membranaccus . , 85 



