348 



FRESH-WATER BIOLOGY 



59 (34) Sexual pore anterior to the middle of the body. Yolk glands branched 

 and either separate or united to form a network. 



Phaenocora Ehrenberg 1836. 

 This is the genus formerly known as Derostomum Oersted 1843. 



Only one species known in this country. 



Phaenocora agassizi von Graff 191 1. 



Length i to 2 mm. Milk-white. Intestine 

 greenish-yellow. Eyes reddish-yellow. Between 

 the eyes and the pharynx or extending over the an- 

 terior end of it there is a zone of so-called crystal- 

 loids which appear clear or grayish-brown in 

 transmitted light. This species is an exception for 

 the genus in that it possesses rhabdites. Pharynx 

 cask-shaped, intestine more or less deeply lobed. 

 In pool, Rochester, N. Y. 



Fig. 617. Phaenocora agassizi. (^) slightly compressed: 

 te, testes; da. intestine; ph, pharyn.x. X 22. (B) An- 

 terior part, enlarged: ^r, crj'stalloids; 6c, bursa copulatrix; 

 mm, muscles of bursa; de-^, proximal, and den, distal part 

 of ductus ejaculatorius; dg, duct of yolk gland; ge, ovary; 

 go, genital pore; rs, receptaculum seminis; au, eye. X 70. 

 (After von Graff.) 



60 (33) With a separate pocket for the chitinous portion of male copulatory 

 organ. Sexual pore lies in last third of body . . Jensenia. 

 Only one species known in this country. 



Jensenia pinguis (Silliman) 1885. 



Length about 1.5 mm. Color 

 brown to reddish, darkest in middle 

 of body. Male genital canal divided 

 at its connection with the common 

 atrium, one branch forming the 

 pocket for the chitinous organ while 

 the other leads to the seminal ves- 

 icle. Rochester, N. Y. 



Fig. 618. Jensenia pinguis. {A) Entire: m, mouth; vi, yolk glands; /, testes; 

 e, eye; ph, pharynx; s, glands; i, intestine. X 30. (After Silliman.) {B) Sexual 

 organs from animal compressed from side: hs, bursa seminalis; bsm, retractor mus- 

 cles of same; ch, pocket which contains chitinous organ; chm, one of four muscles 

 for same; e, egg; gd, oviduct; ge, ovar>'; go, genital pore; sd, shell glands; te, testes; 

 udi, uterus diverticulum of atrium; list, duct of uterus; vd, vasa deferentia; lis, vesi- 

 cula seminalis; vst, duct from same; wgc, female genital canal. X 60. (After von 

 Graff.) 



61 (32) Pharynx rosette-shaped, standing perpendicular to the ventral 

 surface Family Typhloplanidae . . 62 



The genital pore Hes back of the mouth. Ovary one, testes paired. Other parts of sexual 

 organs variable. Protonephridium with two main branches which may have either one or two 

 openings on the ventral surface or may lead to the surface through the mouth or sexual pore. 

 Eyes, non -pigmented light-refracting organs; cihated pits may be present. Rhabdoids play 

 an important part in classification. Both summer and winter eggs produced in some species. 



