^40 FRESH-WATER BIOLOGY 



29 (28) With two very small eyes, yellowish by transmitted light, whitish by 

 reflected light, lying just before the brain in the widest re- 

 gion of the pharynx. . Prorhynchus applanatus Kennel 1888. 



Length 4 mm. White. Bod> 

 much flattened at both ends. 

 Pharynx very muscular. In- 

 testine a slender straight tube 

 with one diverticulum extend- 

 ing anteriorly under the phar- 

 ynx and numerous slender very 

 closely set lateral diverticula. 

 Greenhouse, University of Ne- 

 braska, Lincoln, Neb. 



if-^A 





' '^sqi^s ss.s. Sj.fi- V'^ 



Prorhynchus applanatus. From life. X 20. (After Kennel.) 



30 (3) Female sexual organs divided into ovary and yolk glands. Male sex 

 organs complex Section Lecithophora . . 31 



Ovary in general small and simple. Yolk glands extremely variable, elongated, lobed, or 

 forming a network which anastomoses. Chitinous portion of male copulatory organ very 

 complicated and variable in form. 



31 (74) Proboscis either lacking entirely or if present without a definite 

 sheath Subsection Lipoehynchia . . 32 



This division contains the greater part of the fresh-water Turbellaria. 



32 (61) With a cask-shaped pharynx parallel to the ventral surface or shghtly 

 inclined and with the end directed forward. But one genital 

 pore Family Dalyellidae . . 33 



With the exception of the genus Opistomum, which is not represented in this country, the 

 pharynx is typically cask-shaped and opens into the anterior end of the intestine. The genital 

 pore opens on the ventral surface posterior to the mouth. Ovary simple. Yolk glands variable, 

 female receptaculum seminis and a simple uterus are present. Testes always paired. Chitinous 

 portion of male copulatory organ often very complex. Pigment eyes usually present, but 

 without other sense organs. Protonephridium consists of two principal branches which open 

 on the ventral surface. Rhabdoids and glands of integument prominent. 



SS (60) Without a separate pocket for the chitinous part of the cirrus. . 34 



34 (59) Sexual pore in posterior third of body. The paired yolk glands un- 

 branched and separate. . Dalyellia Fleming 1822 . . 35 



This is the one commonly known as Vortex Ehrenberg 1831. 



