_Figs._ 43, 44, 45, 46, 47, 48, 49, 50, 51, 52. These figures are from drawings made by Major Owen, to illustrate forms of living Polycystina, sketched from life; these convey a faint idea of the richly coloured appearance of the natural structure; _Figs._ 48 to 52--53. Gregarina lumbricorum, round form--54. Gregarina lumbricorum, the usual elongated form--55. Gregarina serpulæ--56. Gregarina Sieboldii; illustration of septate form, with reflexed hook-like processes--57. Gregarina lumbricorum, encysted--58. Gregarina lumbricorum, more advanced and pseudo-navicellæ forming--59. Gregarina lumbricorum, free pseudo-navicella of--60, 61. Gregarina lumbricorum, amœboid forms of--62. Cruciate sponge-spicule--63. Astromma Humboldtii--64. Eözoon Canadense, represents appearance of a portion of the natural size--65. Eözoon Canadense, magnified, showing portions of cell-walls left uncoloured, the animal sarcode inhabiting it coloured dark green as in nature, and converted by fossilisation into a silicious mineral; the narrow bands passing between these are processes (_stolons_) of the same substance--66. Actinophrys sol, budding--67. Euglena viridis: _a._ contracted; _b._ elongated form--68. Acineta tuberosa--69. Œcistes longicornis (Davis)--70. Oxytricha gibba (side view)--71. Oxytricha pellionella--72. Thuricola valvata, expanded--73. Cyclidium (glaucoma)--74. Oxytricha scintillans--75 to 79, 80 to 85, illustrate types of Foraminifera discovered by Major Owen, living--75. Globigerina acerosa, n. sp., broken open to show interior--76. Globigerina, n. sp., broken open to show interior--77. Globigerina hirsuta--78. Globigerina universa--79 and 81. G. Bulloides--80. Conochilus vorticella--82. Globigerina inflata, sinistral shell--83. Pulvinulina Micheliniana--84. P. Canariensis--85. P. Menardii. PLATE IV.--_Page_ 514. METAZOA. BRYOZOA.