34 Papers from the Marine Biological Laboratory at Tortugas. 



The testes were 5 right and 4 left in 8 out of the 11, in the other 3 

 they were 4 right and 5 left. The length of the ova, exclusive of the 

 filament, is about 0.05 and the diameter 0.03 mm. 



This species was found in the following hosts: 



Host, NeomcBnis griseus: 



1906, July 5, II fish, few distomes; July 9, 14 fish, few distomes; 

 July 10, 4 fish, few distomes; July 16, 4 fish, few distomes. 



1907, July 7, 4 fish, few distomes; July 9, 5 fish, 7 distomes; July 14, 

 4 fish, 2 distomes; July 15,5 fish, few distomes. 



Host, Ocyurus chrysurus: 



1907, July 10, 3 fish, I distome. 



1908, June 30, 3 fish, i distome; July 4, i fish, 3 distomes. 

 Host, Calamus calamus: July 10, 1907, 2 fish, i distome. 



Host, Eupomacentrus leucostictus : July 2, 1908, i fish, 2 distomes. 



HAMACREADIUM gen. nov. 



Etymology: ^/^-«, together with; K/ndiV.wy^ a morsel of meat. 



Generic characters: Ventral sucker larger than oral; vitelline 

 glands diffuse, posterior, and lateral; testes 2, diagonal; cirrus-pouch in 

 front of ventral sucker, its base overlapping the ventral sucker for a 

 short distance, or deflected on the right or left anterior border of the 

 ventral sucker; ovary in front of testes, or on right side of anterior 

 testis, lobed; seminal vesicle inclosed in cirrus-pouch; seminal receptacle 

 dorsal to ovary ; uterus usually entirely in front of ovary. 



Hamacreadium mutabile gen. et sp. nov. (Figs. 49-54.) 



Body of great variety of shapes, long-oval under compression, broad- 

 est and often emarginate at posterior end, tapering to anterior end; 

 head and neck sparsely nodular; ventral sucker usually about 1.5 times 

 the diameter of oral sucker; pharynx separated from oral sucker by a 

 short prepharynx; esophagus long and slender; intestinal rami extend 

 to posterior end of body. Genital aperture a short distance in front of 

 the ventral sucker, on the left side of the median line; prostate cells 

 clustered around the ejaculatory duct, most abundant near the genital 

 aperture; cirrus-pouch cylindrical, inclosing the seminal vesicle and 

 lying on the anterior border of the ventral sucker, often extending along 

 the right border of the ventral sucker. Testes 2, in some slightly lobed^ 

 in others tjie lobation was not evident, largely on account of the obscura- 

 tion caused by the vitelline glands. In some specimens which had been 

 killed under pressure the testes were distinctly lobed. The testes are 

 near together and diagonally placed, in some cases about half-way 

 between the ventral sucker and the posterior end, in other cases they 

 are nearer the posterior end. Ovary much lobed, in front of right testis,, 

 the seminal vesicle lying on its dorsal side. The vitelline glands are 

 diffuse, on margins and behind testes, and extend into the neck a little 

 in front of the bifurcation of the intestines. Uterus between the ovary 

 and ventral sucker; ova relatively large. The excretory vessels are not 

 distinct in the mounted specimens. In living specimens a large median 



