no. 3638 TURBELLARIA — KAWAKATSU < 



The color of the dorsal side of the preserved specimens is usually 

 a uniform grayish brown, that of the ventral side a light grayish brown. 

 The situation of the pharynx and the copulatory apparatus may be 

 marked by lighter pigmentation (pi. 1a-f). There are two eyes, situated 

 close together (pi. 1g-i), each enclosed in a small, reniform clear 

 space (pi. 1g). There is a pair of slightly visible auricular sense organs 

 in the usual position (pi. 1g). 



In mature worms the pharynx is situated behind the middle of the 

 body and measures in length almost one-sixth the length of the body. 

 In histological sections, it was observed that the internal muscle 

 zone of the pharynx consists of two layers, circular fibres, and longi- 

 tudinal fibres (characteristic of the family Planariidae). The anterior 

 trunk of the intestine bears five to eight lateral branches; each pos- 

 terior trunk has 10 to 12 lateral branches and many short medial 

 branches in both the pharyngeal and postpharyngeal regions. 4 In many 

 large worms, one to two pairs of medial branches situated at the level 

 of the genital pore are united and form intestinal anastomoses that are 

 located dorsally. Their cavities are lined with the same epithelium 

 as that of the usual intestine. 



The arrangement of the parts of the reproductive system was seen 

 translucently from the whole mount (fig. 2) . The numerous small testes 

 extend in lateral regions from the level of the ovaries almost to the 

 posterior end of the body. Their position is predominantly ventral, 

 below the intestinal branches. Behind the genital pore, they are also 

 found between the two intestinal trunks. In the central cavity of each 

 testis a tangled mass of spermatozoa is found. The two sperm ducts are 

 first noticeable as thin-walled tubular expansions (sperimiducal 

 vesicles) packed with sperm and lying on each side of the pharynx. 

 They are found in a ventral position from the level of the posterior 

 two-thirds of the pharynx to the penis bulb (pi. 1b). 



The two ovaries are of moderate size and typical, each situated 

 behind the first pair of lateral branches of the anterior intestinal 

 trunk. Numerous mature ova occur in the ovaries of the mature 

 specimens. Occasionally, a ball of sperm was seen in a small chamber 

 or ampulla of the ovovitelline duct next to each ovary (i.e., in the 

 seminal receptacle). The two ovovitelline ducts proceed posteriorly 

 in a ventral position and form a common ovovitelline duct at the 

 level of the genital pore. The greater part of the ovovitelline ducts 

 receives the ducts of numerous yolk glands (or vitellaria), the bodies 

 of which are scattered in the surrounding parenchyma. 



4 According to the original description of Phagocata nivea from Alaska, the 

 species possesses 10 or 11 pairs of the branches in the anterior intestinal trunk 

 and 21 to 27 lateral branches in each posterior intestinal trunk (Kenk, 1953, p. 

 165). 



