49] PROTEOCEPHALIDAE — LA RUE 49 



proglottids, 44-52 in young proglottids. Testes arranged in two par- 

 tial layers between vitellaria. Diameter of testes, 0.050-0.090 mm. Va- 

 gina anterior to cirrus-pouch. Near vaginal opening a small sphincter 

 vaginae. Receptaculum seminis anterior to ovary. Passages in inter- 

 ovarial space as in genus. Ovary bilobed, lobes ovoidal, vitellaria 

 sparse, follicles small. Uterus not observed. Two pairs of excretory 

 vessels, ventral and dorsal. Dorsal vessels small, ventral vessels much 



larger. 



Habitat: In intestine of Esox lucius L. (type host) ; Reval, Es- 

 thonia (type locality). 



This species was described and delineated by Gui. Schneider (1905: 

 19-20). La Rue (1911:475) included it in a list of species belonging to 

 the genus Proteocephalus. 



This species from Esox lucius taken at Reval in Esthonia, a prov- 

 ince of Russia, Apr. 30, 1904, is briefly described by Gui. Schneider 

 (1905). Thanks to Dr. H. B. Ward the writer has had some of Schnei- 

 der's preparations and alcoholics for examination. The paucity of 

 alcoholic specimens prevented the use of the section method. The 

 writer has therefore been compelled to be content with a study of toto 

 preparations and specimens cleared in glycerine. The description fol- 

 lowing is based largely on Schneider's data tho wherever possible the 

 writer has introduced his own findings. 



The worms are small and slender 1-4.7 cm. long. A maximum 

 breadth of about 0.7 mm. was observed. No worms had ripe proglot- 

 tids. The diameter of the scolex is about 0.140 mm. The four shallow 

 suckers directed partly forward are weak, small, and about 0.05 mm. 

 in diameter. A vestigial fifth sucker is lacking, tho perhaps a slight 

 thickening of cells in the anterior part of the head is to be considered 

 as the vestige of the shrunken sucker (Schneider). My measurements 

 of a head and its suckers are : breadth 0.140 mm., thickness 0.105 mm., 

 diameter of suckers 0.053 mm., diameter of sucker openings 0.026-0.032 

 mm. A most careful search of Schneider's toto preparation and of the 

 specimen cleared in glycerine failed to reveal a trace of a fifth sucker 

 or vestige of it. The last might not have been visible under these con- 

 ditions. A functional fifth sucker certainly is not present. The suckers 

 are quite prominent, the sucker cavities shallow. The slightly de- 

 pressed head possesses a short flattened tip. The head is not well set 

 off from the neck. Schneider says that the length of the neck is about 

 Yz the length of the body. The writer finds it to be from 2.5-3-4.5 mm. 



Schneider's largest specimen, 4.7 cm. long, was made up of 66 

 proglottids. The youngest proglottids were about twice as broad as 

 long, the middle ones somewhat broader than long, and the posterior 



