THE TURBELLARIA 



classification. Coming to nearer times, the works of Moseley (47), 

 Bohmig (5), Ijima (34), and Yejdovsky (59) will always be con- 

 spicuous for the elaborate and detailed account of the structure 

 of various members of the group. 



As is frequently the case, the study of the habits the Bionomics 

 of the group was begun early, and the observations of some of 

 the older authors still retain considerable value, especially those of 

 0. F. Miiller, Bosc (1801), Dalyell (1814-53), J. K." Johnson 

 (36), M. Faraday (16), on the subject of regeneration and asexual 

 reproduction of Ehabdocoels ; while F. Schulze (53) and C. Darwin 

 (11) give accounts of general physiology and habits respectively. 



Classification of the TurMlaria. The class is divided into three 

 orders, primarily distinguished by the form of the intestine, viz. 

 Ehabdocoelida, Tricladida, and Polycladida. 



ORDER 1. Rhabdocoelida, v. Graff. 



Turbellaria, in which the intestine is a simple, unbranched sac, 

 which may have ill -denned lobes, or the cells of the intestinal wall 

 may, in degenerate forms, give rise to a syncytium which blocks up the 

 cavity. The female gonads are compact, and generally a pair of germaria 

 and vitellaria. (For an account of this order, see especially 22 and 59.) 



SUB-ORDER 1. KHABDOCOELA, Ehrb. Ehabdocoelida, in which the 

 intestine is a simple, straight sac ; variable pharynx ; testes compact ; 

 female gonads variable ; usually without otolith. 



A. Without accessory female copulatory organs. FAMILY 1. MAC- 

 ROSTOMIDAE. Ed. v. Ben. The female gonad is an ovary ; the female 

 pore in front of the male pore. Macrostoma, E. v. B. (Fig. III. 2) ; 

 M. Lemanus, Dupl., is lacustrine ; Omalostoma, E. v. B. ; Mecynostoma, 

 E. v. B. FAMILY 2. MICROSTOMIDAE, 0. Schm. A pair of ovaries present ; 

 asexual reproduction as well as sexual. Microstoma, 0. Schm. (sexes said to 

 be distinct) ; Stenostoma, 0. Schmidt ; both have ciliated pits (see 49) ; 

 Alaurina, Busch. FAMILY 3. PRORHYNCHIDAE, Diesing. The male pore 

 opens in common with the pharynx ; female pore ventral. The female 

 gonad is a single germ-vitellarium. Prorhynchus, M. Schm. (see v. 

 Kennel, 39), (Fig. III. 4, 5). B. With accessory female copulatory 

 organs. FAMILY 4. MESOSTOMIDAE, Duges. Germarium usually distinct 

 from the vitellarium ; pharynx rosulate. a. Monogonoporous. Promeso- 

 stoma, v. Gr., M. 1 ; Proxenetes, Jensen (Fig. III. 3), M. ; Mesostoma, 

 Dug. (Fig. III. 6), F. ; M. JEhrenbergii is the subject of a monographic 

 account by Leuckart (44) ; Castmda, 0. Schm., F. ; Otomesostoma, v. 

 Gr., F. /3. Digonoporous. Byrsophlebs, Jensen, male pore anterior to 

 female ; germarium single, M. FAMILY 5. PROBOSCIDAE, Cams. The 

 anterior end of the body is modified to form a retractile, tactile organ or 

 proboscis. Germaria usually paired, and vitellaria distinct; pharynx 

 rosulate; very complicated penis; usually monogonoporous. Pseudo- 



1 The letter " M " indicates that the genus is Marine and " F " Fluviatile, 



