WORMS. 



ECTOPROCTA. 



Anal opening outside the basis of ttie 

 tentacles. 



Never stalked. A spacious body-cavity. 



(a) Tentacles in a crescent. Fresh- 

 water, Cristatella, Lophopus. etc. 



{h) Tentacles in a circle. Marine, ex- 

 cept Pahidicella. 



Fl-usira, the common sea-mat ; Mem- 

 hranipora, encrusting seaweed, ' etc. ; 

 Cellepora, very calcareous; Alcyonidium, 

 gelatinous. 



Endoprocta. 



Anal opening within the basis of the 

 tentacles. 



The body is stalked. No body-cavity. 

 A pair of nephridia. 



Hermaphrodite. 



Pedicellina, forming colonies as usual. 



Loxosoma, solitary. Both are marine. 



Class Brachiopoda. Lamp-shells. 



The Brachiopods are quaint marine animals which were once very 

 numerous, but are now decadent. The body is enveloped dorsally and 

 ventrally by two folds of skin or mantle, which secrete a shell usually of 

 lime, but sometimes " horny." There is no real resemblance between a 

 Brachiopod shell and that of a bivalve Mollusc, except that both consist 

 of two valves. In Brachiopods these lie dorsally and ventrally, in 

 Lamellibranchs they are lateral ; moreover, in Brachiopods the ventral 

 valve is usually the larger. It is hardly necessary to say that the Brachio- 

 l^od organism is not the least like a Mollusc. 



From the mouth region arise ciliated tentacles, or two long "arms" 

 coiled in a spiral and often supported by a calcareous skeleton. The 

 ciliated food-canal ends blindly, or near the mouth, except in Crania 

 where it is posterior and dorsal. There is a nerve-ring round the gullet 

 with a slight brain and inferior ganglion. Sensory structures, in many 

 cases, perforate the valves. It is probable that a heart lies above the 

 gut, and is connected with blood vessels. Two (or more rarely four) 

 nephridia open near the mouth, and serve also as genital ducts. The 

 posterior region of the body often forms a stalk by which the shell is 

 moored, but in many the stalk is absent, and the animal is directly attached 

 to the substratum. The sexes are sometimes separate, but perhaps some 

 are hermaphrodite. There is a metamorphosis in the development, of 

 which however little is known. 



Testicardines. 



EcARDINES. 



The valves are hinged. 

 There is no anus. 

 Terebratiila. Waldkehnia. 



There is no hinge. 

 There is an anus. 

 Crania. 



Litigula, persistent since Palaeozoic 

 ages. 



