XIV 



List of Illustrations. 



Pig. 



226. Pulesc irritant 



227. Diagram of the anatomy of a Spider . 



228. Alimentary canal of a Spider 



229. Sexual apparatus of one of the Phalangiidse 



230. A Scorpion . 



231. Diagram of the anatomy of a Tyroglyphus . 



232. Female of Pentastomum tsenioides . 



233. Pycnogonum 



234. Diagrammatic figure of a Tardigrade . 



235. Portion of the radula of a Cephalopod . 



236. Diagrammatic longitudinal section of the mouth of a Gastropod 



237. Diagram of the central nervous system in various Mollusoa 



238. Chiton 



239. Diagraanmatic figure of a Gastropod 



240. Diagrams of various forms of Gastropod shells .... 



241. The shells of two examples of a tropical land Snail 



242. Shell of a Snail (Paludina) 



243. Diagram of the nervous system in relation to the alimentary canal 



244. Male Periwinkle . . 



245. Female Periwinkle 



246. Diagram of the genitalia of various Gastropods .... 



247. Larva of a Gastropod . . 



248. Carinaria ... . .... 



249. CUodora ... . . 



250. Cleodora ......... 



251. Pneumodermon 



252. A transverse section through a Lamellibranoh ■ . . . 



253. Transverse sections through two Lamellibranchs . 



254. Lamellibranoh removed from the shell 



255. Tapes decussatus ........ 



256. Eight sheU valves of two different Lamellibranchs 



257. Diagrammatic transverse sections through the shell of Lamellibranchs 



with internal (A, A') and external (B, B") ligaments 



258. Diagrammatic longitudinal section of a Lamellibranoh 



259. Larvae of Oardvum . . ... 



260. Mya arenaria . ... . . 



261. Teredo navalis 



262. Diagram of a decapodous Cephalopod 



263. Nautilus 



264. Diagrammatic figures of various Cephalopod shells 



265. Diagrammatic transverse sections through the eyes of various Cephalopoda 



266. Diagram of the heart, etc., of a Cephalopod 



267. An ootopodous Decapod in which the heotocotyUsed portion of the right 



arm is very well developed 



268. Diagrammatic fig^es to illustrate the relations between the Chitons and 



the Cephalopods . . 



269. Diagram of a vertebra and the parts connected with it ... . 



270. Diagram of the skeleton of the fore-limb of a higher Vertebrate 



271. Longitudinal section of a joint 



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