Manchester Memoirs^ Vol. xlviii. (1903), No. 4. 13 



b. Penis single, a pair of small widely separated tentacles. 



Pericelidce. (:02). 

 B, No marginal eye-spots. 



a. Prostate developed on the walls of the antrum. 



DiposthiidcR ('97). 

 II. Pharynx in front of the middle of the body. 



A. Pharynx folded. Pseiidoceridce. 



B. Pharynx tubular. 



a. Tentacles usually present, prostate as in Pseudoceridcz. 



EiiryleptidcB. 



b. No tentacles, a pair of prostatic vesicles. 



Prosthiostomidce. 



C. Pharynx reduplicated, body very long and narrow (no 



sucker ?) Diplopharyngeatidiz ('96). \ 



III. — Notes on the Tables. 



Note A. — The remarkable diverticulum of the vagina found 

 in Paraplanocera, which I have figured elsewhere {'.02, fig. 63), is 

 quite without a parallel in any other known genus. Verrill ('88) 

 in describing his new genus Eustylochus speaks of a long median 

 duct which opens at the female orifice and runs forward to end 

 in a flask-shaped vesicle. With this he compares a structure 

 found in Stylochoplana maculata. 



A careful examination of de Quatrefages' beautiful figure of 

 this species ('45,//. wi.,fig. 2) has, however, convinced me that 

 in this species at any rate, this median duct is nothing more than 

 the anteriorly directed vagina (the uteri are shown opening into 

 it) continued forward into the accessory vesicle. The fact that 

 de Quatrefages has figured the narrow forwardly directed part of 

 the vagina opening at the female orifice and not into the upper 

 end of the wide distal part of the vagina is, I think, readily to 

 be accounted for by the difficulty of determining the precise 

 course of a duct bent upon itself, by means of optical sections 

 only. I have not been able to examine sections of Stylochoplana 

 maculata., but I feel convinced that when the genital organs of 

 this species are so studied they will be found to resemble in detail 

 those of Stylochot>la7ia agilis as figured by Lang ('84, pi. 30, 

 fig- 13)- 



