308 T. B. ROSSETER OX HYMENOLEI>IS FARCIMINALIS. 



We will assume that the investigator is acquainted with 

 Hymenolepis serpentulus from the fact of his having found this 

 avian tape-worm and studied its anatomy ; or, if not, that he is 

 at least acquainted with Von Linstovv's work on Taenia serpen- 

 tidus. I have selected H. serpentulus because both generically and 

 specifically there is an affinity, in some points morphologically, 

 between this species and H. farciminalis. But if we select the 

 receptaculum seminis as a point for comparison, we shall at once 

 be convinced that in the segments before us we have not II. serpen- 

 tulus. The receptaculum of H. serpentulus is a large, irregular, 

 pear-shaped sac. Its anterior portion measures 0*37 mm. and 

 its posterior 0"18 mm. in diameter, and, to quote Von Linstow, " sie 

 1st das grosste Organ in der Proglottides Compare this with the 

 description given above of the same organ in the segments under 

 consideration, and it is sufficient to convince us that our specimen 

 is not H serpentulus. 



Again, the question may be asked : "Is it necessary to base our 

 conclusions on structural internal characters for the determina- 

 tion of a genus and species of the Cestoidae ? " 



It certainly is so, in the absence of the hooks of the rostellum, 

 either by caducity, or, as so often occurs, by the scolex being left 

 in the mucous membrane of the intestine; or, again, from the 

 species being inerme, as in the case of Taenia {Hymenolepis) 

 megaloon, Von Linstow (St. Petersburg, 1901). 



For more than a century and a quarter this tape-worm has 

 been known to helminthologists as Goeze's (Batsch's) Taenia 

 farciminalis. Itailliet, following Blanchard, and, like Weinland, 

 recognising the fact that something more distinctive was required 

 in diagnosing the various species embodied collectively in the genus 

 Taenia, formulated the genera Dicranotaenia, Drepanidotaenia, and 

 Bothriotaenia. From the formation of the hooks on the rostellum, 

 farciminalis falls, as serpentulus would, into the first of Bailliet's 

 genera ; and we should classify it as a Dicranotaenia, and turn to 

 Krabbe's Bidrag for figures of the hooks to determine our species. 

 But this classification of Railliet's only partially meets the case, 

 as if the hooks are absent we require some other character in 

 order to recognise the genus to which our species belongs. 



