NO. 1123. 



PBOCEEDINGS OF THE NATIONAL MUSEUM. 



799 



8. RHYNCHOBOTHRIUM HETEROSPINE, Linton. 



(Plate IV, tigs. 3-8.) 



Rhynchohothriuin Inter ospina, IjINTON, Fish Com. Rept., 1887, p2>. 83!>-84(), pi. 

 XII, figs. 3-.5 (not 6). 

 Some cysts from the peritoneum of tbe common eel [AnguUla rostrata), 

 collected at Woods Holl, Massachusetts, September 2, 1885, contain 

 embryos which agree in the character of the hooks, the best criterion 

 for determining- species in these soft-bodied worms, with R. hcierospiyie. 

 Two specimens in alcohol: 



MeasHrcmenIs of lihynchobothriam heterospine. 



Length 



Breadth of head 



Diameter of neck 



Lengtli of bothriTim 



Length of contractile bulbs 



Length of proboscis, approximate 

 Lengtli of longest hooks 



The retractor muscle of tlie i)roboscis is attached to the inner wall of 

 the contractile bulb uear the anterior end (tigs. 6, 7). 



It can hardly be inferred that the eel is the true intermediate host 

 of this parasite. This remark may indeed be properly made for many 

 of the larval parasites found iu fishes — where they may be in tlie con- 

 dition of what Beneden calls xenosites or strangers. 



When a blastocyst was removed from its cyst, it was enveloped in a 

 thin hyaline membrane (fig. .">, //). After the embryo was removed from 

 the blastocyst, the latter exhibited signs of life for some time, even 

 attaching itself to the bottom of the glass vessel by its smaller end and 

 dragging itself along. 



The embryo when liberated from its blastocyst, had the following 

 dimensions, living: Length, li.l mm.; breadth of head, 0.49; length of 

 head, 0,35; diameter of neck, 0.21; length of neck from base of bothria 

 to base of contractile bulbs, 0.04; length of contractile bulbs, 0.42. 



The retractor of the proboscis attached to wall of contractile bulb 

 near anterior third of bulb. 



9. RHYNCHOBOTHRIUM IMPARISPINE, Linton. (Larva.) 

 (Plate IV, figs. 9-12.) 



liln/nchohothritim imparisp'ine, U. S. Fish Com. Eept., 1887, ]>p. 840-843, pi. xii, 

 figs. 6-9. 



Following is a list of finds of a tetrarhynch, which I have identified as 

 R. imparispine. The principal criterion used in these identifications 

 has been the nature and arrangement of the hooks on the proboscides, 



