TREMATODES FROM FISHES LINTON 71 



tinuous. Average of four in balsam: Testes in breadth, 2; oral 

 sucker in ventral sucker, 1.63 ; pharynx in ventral sucker, 3. 



On July 11, 1927, five distomes were collected from a sea raven 

 measuring 20 cm. in length. These, mounted in balsam, are seen to 

 taper rather uniformly from about the level of the ovary to the 

 posterior end. In one the seminal receptacle is situated at the left 

 anterior border of the ovary; in the other it is greatly enlarged, the 

 ovary being compressed between it and the first testis. It measures 

 0.16 mm. in length and 0.23 mm. in breadth. In another the ovary 

 is crowded to the right side of the body by a mass of yolk, the yolk 

 reservoir being greatly distended. The greatly reduced seminal ves- 

 icle in this specimen lies along the left side of the yolk reservoir. 

 The latter is pyriform, length, 0.28 mm., greatest breadth, 0.17 mm. 

 The ovary, length, 0.18 mm., breadth, 0.14 mm., is crowded into a 

 triangular space at the anterior left border of the first testis. In 

 three of these specimens the esophagus about equals the pharynx 

 in length, in the other it is a little longer than the pharynx. 



Recorded from the conger eel : Linton, Bull. U. S. Fish Comm. for 

 1899, p. 436, 1901. 



Recorded from the tomcod : Linton, Proc. U. S. Nat. Mus., vol. 20, 

 p. 526, 1898 ; Bull. U. S. Fish Comm. for 1899, p. 475, figs. 331, 332, 

 1901. Collected from this host on 116 dates in 13 different years; 21 

 dates in January, 10 in February, 2 in March, 36 in April, 6 in May, 

 2 in June, 4 in July, 1 in August, 5 in September, 12 in October, 5 in 

 November, and 12 in December (U.S.N.M. No. 8236). All collections 

 with the exception of those in July and August made by Vinal N. 

 Edwards. These distomes vary greatly in length and shape. Most 

 of those preserved in formalin vary in length from less than 1 to 6 or 

 7 mm., but slender, elongate forms occur that measure as much as 12 

 mm. Most of them are linear with prominent ventral suckers and 

 with vitellaria interrupted opposite the testes. It should be noted, 

 however, that living forms which are thickish, with closely appressed 

 testes and unbroken vitellaria, may change, under pressure of the 

 cover glass, to slender, elongate forms with vitellaria interrupted at 

 the level of the testes. Also, when placed in fresh water, they become 

 turgid, lengthened, and cylindrical, the acetabulum prominent and the 

 neck reflected dorsally. The same changes follow immersion in weak 

 formalin. Only one case was noted in which the ovary was not dis- 

 tinctly lobed; usually the ovary is 3-lobed at the posterior end, with 

 a single anterior lobe, like the handle of a pestle. The testes in a few 

 cases were slightly lobed. But one case was noted in which the body 

 wall formed a raised margin around the ventral sucker. The number 

 of fishes examined was not recorded in every instance. Following 

 is a summary of collections in which the number of fishes examined 

 was recorded: 



