complete resemblance although the number of cells in P, integerrimum is 

 somewhat smaller and their location is such that we prefer to speak of three 

 and not five zones of ciliary epithelium. There is no doubt that the 5 zones 

 of cells in D. ranae represents the next step in the differentiation of the 

 ciliary epithelium. This is seen especially clearly in the examination of 

 D. ranae from the dorsal surface (Fig. 211). For we can observe from 

 that view the rapprochement between the first and second, third and 

 fourth groups of ciliary cells, i.e. , their three-zoned distribution. 



There are 2 pairs of pigmented eyes located at the end of the 

 first third of the body. The digestive system is represented by the 

 barrel-shaped pharynx located posteriorly to the eyes, by a short esophagus 



and two intestinal trunks which end 

 blindly without extending into the 

 attaching disc. The excretory 

 system (Fig. 212) of D. ranae was 

 studied by Ozaki fairly accurately. 

 It is of the same type as among 

 Polystoma. It is well-developed. 

 The excretory openings lie dorsally 

 along tl^ sides of the body at the 



189 



Fig. 212. Diplorchis ranae Ozaki, 

 excretory system of a free- 

 swimming larva. (According to 

 Ozaki, 1935). 



Fig. 213. Diplorchis ranae Ozaki, 

 attaching armature of the disc of 

 the free -swimming larva. 

 (According to Ozaki, 1935). 



level of the esophagus. The attaching armature (Fig. 213) is represented 

 by 16 lateral hooks lying along the edge of the disc and by 2 middle hooks. 

 The lateral hooks are of the same type as among Polystoma , but are of two 

 sizes. The first 7 pairs are small, 0. 017 - 0. 02 mm in length and the 

 8th pair is almost twice as large — 0. 034 - 0. 038 mm. The middle hooks 

 have the shape of straight needles, slightly thickened near the lower 

 terminal; their length is 0. 022 - 0. 027 mm. Further development of D. 

 ranae has not been studied but apparently proceeds as among Polystoma . 

 The presence of a gill form is unknown. 



205 



