28 -^'^^- 3- — 'i- Kaburaki : 



species. Close to the pigment cup thete exist some ganglionic 

 cells, the processes of which on one side proceed towards the brain 

 and on the other pursue a course to connect witli the retina cells. 

 The cells number three or four? in Pr. lactea and St. trigonoce- 

 phala, but two only in Ect. UmuU. As stated by several authors, 

 they exhibit generally the fibrillous structure. In the proximal 

 part of the retina cones are seen very weakly stainaljle fibres, 

 which show a decreasing aflSnit^^ for stains as we recede from the 

 proximal part. The fibres are at length connected witli " Stift- 

 chen " which is deeply stainable. 



Reproductive System. 



Male Organs. 



The male organs are composed of the testes, the vasa defer- 

 -entia and the penis. 



Testis. — In the marine Triclads there is a wide degree of 

 variation in the number of testes. Böhmig describes in Pr, ohlini 

 and Bd. Candida 100-150 on either side of the body; while 

 WiLHELMi (71) records in Cerbussowia cerruti only a single pair of 

 them, the smallest number of which I Iiave found any record. 

 Among the species examined, Pr. lactea bears 58 testes on either 

 side, St.trigonocephala o0-35, tlie average number being 32, and 

 Ect. limuli 18. 



The testes show a considerable variation in position and 

 arrangements. In Pr. lactea they are situated in the dorsal part 

 of the body-parenchyma and are arranged in two lateral zones 

 extending from the ovarian region backwards nearly to the body- 

 end. In St. trigonocephala they are found lying ventrally not only 

 on both sides of the longitudinal nerve trunks from cluse behind 

 the ovaries to the insertion of the pharynx, but also posteriorl3^ 

 only on the outer side of the same, ceasing altogether to exist at 

 about the level of the mouth. In Ect. UmuU they are placed in 

 the ventral part along both sides of the anterior unpaired gut 

 trunk, extending backwards up to the dividing point of the gut 

 trunks, (lonerally the testes are situated on either dorsal or 



