LIST OF ILLUSTRATIONS 



30. Transverse section through a polyp of Alcyonium digitatum 



below the level of the oesophagus ..... 70 



31. Transverse section through a polyp of Alcyonium digit atum 



through the region of the oesophagus .... 70 



32. Semi-diagrammatic view of half a simple Coral ... 73 



33. Aurelia aurita ...... ... 76 



34. Strobilisation of Aurelia aurita ...... 77 



35. Hormiphora plumosa ........ 79 



36. View of a branch of Leucosolenia showing sieve-like mem- 



brane which stretches across the osculum ... 85 



37. Vertical section through an osculum with sieve-like mem- 



brane, and a tube of Leucosolenia ..... 86 



38. Section of a flagellated chamber oiSpongilla lacustris, showing 



the flagella and collar cells ..... . 87 



39. Section of a portion of Grantia extusarticulata . . . 88 



40. Two flame-cells or solenocytes from the nephridium of an 



Annelid worm ......... 93 



41. Mesostoma splendidam, drawn from a compressed individual ; 



the cilia and rhabdites are omitted . . . . . 95 



42. Planaria polychroa, with everted proboscis . . . .100 



43. Diagram of the reproductive and nervous systems of a 



Trematode, Distomum hepaticum ..... 102 



44. Diagram of the digestive and excretory systems of a Trema- 



tode, Distomum hepaticum ...... 104 



45. A Tape-worm, Taenia solium . ..... 1 07 



46. Transverse section through a mature proglottis of Taenia. 108 



47. Diagram of a ripe proglottis of Taenia solium . . . 109 



48. Lineus geniculatus . . . . . . . . . 114 



49. Cerebratulus fuscus. Young transparent form . . . 116 



50. A Rotifer, Floscularia ; (a) female of Floscularia cormda, 



(b) male of Floscularia campanulata . . . . 120 



51. Diagram of Floscularia ......... 121 



52. Diagram of a Rotifer . . . ..... 123 



53. Hydatina senta. Ventral view ...... 124 



54. Female Ascaris lumbricoides cut open along median dorsal 



line to show the internal organs ..... 128 



55. Male Ascaris lumbricoides cut open along the dorsal middle 



line ........... 130 



56. Trichina spiralis, encysted amongst muscular fibres . . 131 



57. Three transverse sections through a developing Amphioxusio 



show the origin of mesoblast from endodermal pouches . 134 



58. Two stages in the early development of a common fresh-water 



mollusc, Planorbis, to show the origin of the mesoderm 



cells ........... 135 



59. Latero- ventral view of an Earthworm Lumbricus terrestris . 139 



