766 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [48] 



9. Echeneibothrium variabile Van Beneden. 



[See Report of U. S. Commissioner of Fish ind Fisheries for 1886, pp. 460-462, Plate 

 I, Figs. 9-13, for description and synonymy.] 



I have already noted the occurrence of this parasite in the common 

 skate (Raia erinacea). Since the description which is referred to above 

 was published, I have found this Echeneibothrium on two different oc- 

 casions. On August 29, 1887, I examined twenty-four skates. Their 

 stomachs were filled with small Crustacea, for the most part Crangon 

 vulgar is. Some of them contained, beside these, a few Annelids, such 

 as Nereis and Rhynchobolus. Many of the skates had no parasites. 

 About a half a dozen specimens of E. variabile and one specimen of 

 Rhynchobothrium erinacens were obtained from the spiral valve and a 

 few Nematods from the stomach and spiral valve of a few. On Sep- 

 tember 6, 1887, 1 examined ten skates and obtained from the lot four 

 specimens of E. variabile. 



I add the following data, based for the most part on notes made 

 while observing the living worms. 



The following measurements are from one of the living specimens of 

 the first lot : Length 5o mm ; length of bothrium, including pedicel, vary- 

 ing with contraction from .5 to l" uu ; diameters of face of bothrium .24 mm 

 and .6 mm ; diameter of myzorhynchus at base about .26 mm , length .OS tnm ; 

 diameter of neck .14 mra ; distance to first segment i.4 mm ; length of first 

 segment .025 mm , breadth .16"""; length of median segments .3 mm , breadth 

 ,22 mm ; length of last segment 1.2G mi ", breadth .42""". 



The segments were transversely rugose. The head was opaque, 

 ivory white ; central core of neck also dense, opaque, white for .4 mil! back 

 of head. When placed in Perenyi's fluid this specimen shrunk to 30 mm . 

 Another specimen in the second lot was first placed in fresh water, then 

 transferred to alcohol; it measures as an alcoholic specimen 14 mm . It 

 was not measured while living, but it did not shrink so muck as the 

 specimen which was killed in Perenyi's fluid. 



It is very difficult to ascertain the exact number of the loculi on the 

 face of a single bothrium. The plan of arrangement, however, seems 

 to be as follows : Three transverse costre and a middle partition divide 

 the face of each bothrium into about eight loculi. Of these, three pairs 

 are median and two single loculi are terminal. The bothria, although 

 undoubtedly capable of expanding broadly, have a tendency to contract 

 and close up by the appression of the sides and ends, and this too when 

 first placed in sea-water. Some of the specimens are so much contracted 

 as almost entirely to conceal the bothrial cortre. None of the specimens 

 in these lots showed the posterior elongation of the head noted and fig- 

 ured in my former paper. One specimen, measuring 27 nn " in length, was 

 not so active as the others; moreover no loculi could be discerned, 

 although the general appearance of the head was the same as that of 

 the others. The last segments, which were about .6 mm long and .4 m 



