222 RESEARCHES IN HELMINTHOLOGY AND PARASITOLOGY. 



tion the posterior portion becomes more or less annularly constricted. 

 In greatest activity the head is protruded and the body greatly elon- 

 gated, and alternately shortens and elongates. With elongation 

 the annular appearance of the posterior part entirely disappears. 

 The rostellum and bothria are incessantly protruded and retracted 

 and become more or less ov^al in form. In the quiescent state, by 

 transmitted light, the head appears as a nearly central clearer spot 

 embraced at the sides by the pigment streaks. When the bothria 

 are protruded, the latter are situated posterior to them. 



The body of the Scolex is filled with the usual oval, clear, sharply 

 defined corpuscles. Under moderate pressure the water vascular 

 system is brought into view. This appears as a tortuous vessel, 

 proceeding forward on each side of the body from a little terminal 

 caudal vesicle, returning from the head where it forms an expanded 

 loop on each side of the rostellum. 



With the Scolcx as described there were found some smaller indi- 

 viduals having the same characters, but without the conspicuous 

 pigment streak. 



The Scolex of the Shad and Herring has a near resemblance to 

 the Scolex polytnorpJms, Rudolphi, and it ma}', perhaps, prove to be 

 the same. This species is described as having the bothria divided 

 by a transverse partition, which is not the case in the Scolcx under 

 consideration. Van Beneden, however, represents forms of the 

 ^. polymorpJms of the Turbot, without the division of the bothria 

 (Mem, Acad, de Belgique, xxv, pi. i. Figs. 1-3). 



The mature tapeworm of the Scolcx of the Shad and Herring is 

 yet unknown and no doubt has for its host some animal that appre- 

 ciates these fish for food quite as much as man does. 



[May, 1888. No. 565. See Bibliography.] 



Parasites of tJie Pickerel. — Dr. Leidy remarked that among the nu- 

 merous parasites which are mentioned as infesting the Pike, Esox 

 Indus, of Europe, no Tivnia is indicated. In the Pickerel, Esox 

 reticulafus, brought to our market, a species of the latter appears 

 to be common. In two fishes he found half a dozen in the intestine 

 and .stomach ; and in another a single individual two feet in length. 

 It resembles closely the Tcrnia aDiblopliiis, noticed in the Rock Bass, 

 Ainbloplitis rupestris (Proc, 1887, 23), and may be the same. Dis- 

 tingui.shing it with the name of Tcenia leptosoj/ia, its characters are 

 as follows : Body long and thin, and at the forepart thread-like. 

 Head unarmed, without rostellum, with four equidistant hemi- 

 spherical bothria ; neck very short or none ; anterior .segments 



