67] PROTEOCEPHALIDAE — LA RUE 67 



glycerine, from specimens stained and mounted in toto and from trans- 

 verse and frontal sections. 



These cestodes are small and slender (Fig. 32). The largest speci- 

 men from the Sebago Lake material measured 90 mm. long by 1.24 mm. 

 in maximum breadth. The longest specimen from the Walnut Lake host 

 measured 66 mm. long by 1.0 mm. in maximum breadth. The strobila of a 

 50 mm. specimen is made up of an unsegmented neck 3-7 mm. long by 

 0.20-0.25 mm. broad followed by 300 proglottids. The youngest proglot- 

 tids measure about 0.050 mm. long by 0.250 mm. broad. Further along 

 in the chain these increase in length and breadth until in mature and 

 ripe proglottids the length and breadth are about equal. Measurements 

 of several ripe proglottids are as follows, the length in millimeters being 

 stated first: 0.595 by 0.595, 0.680 by 0.680, 0.595 by 0.663, 0.730 by 

 0.595 mm. In transection the proglottids are elliptical. 



A typical functional end-proglottid with a rounded posterior end 

 is present. The segmentation is not very plain, for the inter-segmental 

 furrows are not deep and the corners of the proglottids do not project. 

 The lateral margins are rounded and smooth. The head (Figs. 29-32, 

 35, 36) is a cone-shaped structure somewhat flattened dorso-ventrally. It 

 is not marked by folds or furrows. Its breadth is about 0.33 mm., its 

 thickness about 0.22 mm., its length about 0.20-0.25 mm. In extreme 

 cases the head may attain a breadth of 0.45 mm. This extreme breadth 

 is due to a contraction of the longitudinal muscles of the head and neck. 

 A collection of these specimens shows heads of very different states of 

 contraction. The head bears on its broadest part four deep cup-shaped 

 muscular suckers which are directed forward and outward. On its apex 

 the head bears a well formed muscular fifth sucker. The diameter of 

 the suckers ranges from 0.095-0.105 mm., while the diameter of the 

 aperture varies from 0.06-0.07 mm. The fifth sucker measures 0.05-0.075 

 mm. in diameter. Altho its cavity is quite shallow it has the appearance 

 of being functional for it possesses a typical musculature ( Fig. 93 ) . 



The cuticula and musculature have not been found to differ in their 

 essential features from those of other members of the genus. The ner- 

 vous system in the head is much like that of Ophiotaenia filaroides. A 

 ganglionic mass is located at the level of the suckers (Fig. 93). Two 

 main lateral nerve trunks extend throughout the length of the strobila. 

 No accessory nerve trunks were observed. 



The excretory system in the head is made up of four main longi- 

 tudinal canals which at various levels receive many anastomosing coiled 

 vessels which pass through the tissues of the scolex and neck in every 

 direction. In the strobila there are two pairs of lateral excretory ves- 

 sels, ventral and dorsal respectively. These lie within the medullary 



