[37] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 489 



length of the specimen, when stretched out by fastening one end with a 

 needle to the bottom of the dissecting dish and removing all kinks and 

 curves with a fine brush, was 170 mm . The length of the same speci- 

 men, after having been preserved in alcohol, is less than 90 mm . The 

 specimen when first obtained and placed in sea- water was quite active. 

 The body was constantly throwing itself into sinuous curves, while the 

 head and neck were jerked from side to side with a moderately rapid 

 motion. In addition to these movements the neck and anterior por- 

 tions of the body constantly changed their shape by the inflation or 

 dilatation of the investing membranes into wide transparent folds, con- 

 stricted at irregular intervals by narrow transverse bands. The neck, 

 meanwhile, was alternately stretched out and contracted like the body 

 of a Nemertean. The anterior end of the head protruded into a pro- 

 boscis-like papilla. The breadth of the head itself varied from 0.17 mm 

 to 0.35 mm . 



In the alcoholic specimen the dilatable folds of the neck are much 

 contracted and broken. They lie in rough, ragged frills along each side 

 of the dark central part of the strobile. The head is truncate or blunt 

 in front. The neck immediately behind the sucking-disks is almost as 

 wide as the head, flat, thin, and little, if at all, tapering. 



The following measurements were made on the living specimen. The 

 head and neck changed their position and shape so rapidly that it was 

 with the greatest difficulty that trustworthy measurements could be 

 made : 



Millimeters. 



Breadth of head 0. 28 



Diameter of acetabula 0. 12 



Diameter of neck, narrowest part 0. 20 



Distance of first segments from bead 17. 00 



Length of fourth segment from end of strobile 1. 30 



Breadth of same, posterior end 1,50 



Breadth of same, anterior end 1.00 



Length of posterior segment 0.90 



Breadth of same, posterior end 0. 60 



Breadth of same, anterior end 1. 25 



Habitat.— Common Eel (Anguilla vulgaris); intestine; Wood's Holl, 

 Mass., August 2G, 1885; one specimen. 



Von Linstow (Compend. der Helminth., 1878) records but two Tocniaz 

 from the Common Eel, T. macrocephala Crepliu and T. hemisph erica Mo- 

 lin. T. dilatata is very different from the former. Diesing (Revis. der 

 Ceph., Ab. Cycl., p. 378) mentions the latter, but gives no enumeration of 

 characters. I do not have access to Molin's paper, and cannot, there- 

 fore, say whether T. dilatata is identical with his species or not. The 

 peculiar inflated character of the neck suggests T. ambigua Dujardin, 

 but the difference in size between the adult specimens is alone sufficient 

 to render their union in the same species impossible. 



