THE TURBELLARIA 



ii 



/ 



FIG. III. Rhabdocoelida. 



l.Graffilla muricola, v. Jlier., parasitic in certain marine molluscs, ventral view, a/mouth ; 

 *, three of the four lobes around the body the ventral lobe overlaps the genital pore (un- 

 lettered) ; the penis, which opens through the same pore as the female ducts, is indicated by 

 the shaded circle ; c, the left uterus ; d, the intestine. 



2. Macrostoma hystrix, Oerst. (modified after v. Graff), as an example of a " digonoporous " 

 Rhabdocoel. Sensory hairs are scattered over the body ; and the peculiar fish-like tail carries 

 a number of adhesive papillae, a, streaks of rhabdite cells; b, mouth, leading into the 

 pharynx, immediately in front of which is the brain, on which lies a pair of eye-spots ; c, the 

 intestine ; d, the female genital pore ; e, the male pore ; /, the penis, which consists of a 

 glandular mass and a curved chitinous spine (black in the figure). 



3. Proxenetes rosaceus, v. Gr. (modified from v. Graff), as an example of the " mpnogono- 

 porous " condition, o, streaks of rhabdite cells ; b, brain ; c, eye ; c, ovary, which is here a 

 " germ-vitellarium," in which the upper part of the organ gives rise to yolk cells, and the lower 

 part to egg cells, /; g, the genital atrium ; h, genital pore ; i, bursa seminalis or spermatheca, 

 here an evagination of the atrium, but functionally is part of the female system ; j, seminal 

 vesicle, containing spermatozoa ; it is a dilatation of the conjoined sperm ducts ; k, chitinous 

 tube around the penis ; the glandular pail of which is indicated by the dotted area ; I, sperm 

 duct ; m, testis ; n, mouth, leading into the rosulate pharynx. 



l.Prorhynchus fontinalis, Vejd. (after Vejdovsky). a, terminal mouth ; b, lateral, ciliated 

 pit ; c, the pharyngeal sac ; d, the long tubular pharynx in a condition of rest ; e, its aperture 

 the functional mouth ; /, intestine. 



5. The anterior end of the same Turbellarian, showing the pharynx in the course of eversion 

 .(letters as before). The pharyngeal introvert is acrecbolic. 



6. Mcsostoma lingua, O. Schm. (after v. Gr.), external view, a, mouth, leading into the 

 pharynx ; b, the common genital pore. The two black dots in front of the mouth are the eyes. 



7. Outline of Vorticeros (after v. Gr.). o, tentacular prolongations of the body. 



8. Cylindrostoma quadrioculatum, Jens. A median -longitudinal section (after Bohmig) 

 exhibiting a common oro-genital pore ; and the independent, dorsally situated spermatheca. 

 a, cephalic glands ; 6, brain ; c, testis ; d, yolk-producing region of the germ-vitellarium ; e, 

 intestine ; /, pore of spermatheca ; g, spermatheca filled with spermatozoa ; h, penis ; h', its 

 opening into the atrium ; i, opening of the female duct into the atrium ; j, genital atrium ; 

 k, tubular pharynx, lying in its pharyngeal sac, dorsal to the genital atrium ; m, common 

 pharyngo-genital chamber ; n, oro-genital pore. Specialised epidermal unicellular glands are 

 shown opening near this pore, and others into the base of the pharynx. 



9. Allostoma. a, ciliated band behind the head (cf. the ciliated pits of Prorhynchus), which 

 carries four eyes ; b, the intestine ; c, germarium ; d, pharynx, in its pharyngeal sac ; e, penis, 

 which opens into a genital atrium, communicating with a common " pharyngo-genital chamber"; 

 /, the "oro-genital pore." 



