56 Papers from the Marine Biological Laboratory at Tortugas. 



Host, HcBmulon sciuriis: 



1907, June 28, I fish, i distome; July i, i fish, i distome. 



Dimensions, balsam: Length 0.65; breadth 0.43; oral sucker o.ii; 

 pharynx 0.04; ventral sucker 0.33; ova 0.034 by 0.017. This specimen 

 is shown in fig. 124. 



1907, July 5, 6 fish, I distome. 



1908, July 7, I fish, I distome. 



Dimensions, Hfe: Length 1.82; breadth 0.98; oral sucker 0.15; 

 pharynx 0.07; ventral sucker 0.49; ova 0.037 by 0.020. 



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



Dimensions: Length 0.84; breadth 0.42; oral sucker 0.12; pharynx 

 0.05; ventral sucker 0.28; ova 0.031 by 0.017. 



Dichadena acuta gen. et sp. nov. (Fig. 127.) 



Etymology: '^!/«, in two; aor'f-', gland. 



Body smooth, fusiform but tapering more toward anterior than 

 posterior end, greatest breadth back of ventral sucker; neck conical, its 

 length but little exceeding the diameter of the ventral sucker; oral 

 sucker sub ventral, its diameter scarcely equal to one-third the ventral 

 sucker ; pharynx short-pyriform adjacent to oral sucker; esophagus appar- 

 ently none; intestinal rami obscured by the enormous number of ova 

 but probably extending to, or nearly to, the posterior end. Genital 

 aperture on median line about half-way between the suckers; cirrus 

 short ; cirrus-pouch oval and containing numerous cells. From this oval 

 pouch a long prostatic tube passes diagonally to the left margin, extend- 

 ing farther caudad than the posterior margin of the ventral sucker. The 

 prostatic tube is clavate, increasing in size gradually to the posterior 

 end, and the prostatic cells are confined to the posterior half of the tube. 

 At the caudal end of the prostate there is an oval seminal vesicle which 

 is sharply marked off from the prostate. A short vas deferens leads back 

 from the seminal vesicle to the testes, which are two in number, one fol- 

 lowing the other and contiguous to each other. They lie near the left 

 margin and about half-way between the ventral sucker and the posterior 

 end. The ovary lies on the median border of the posterior testis. It is 

 oval and its longer diameter is transverse. The shell-gland is on the 

 dorsal side of the ovary, in ventral view appearing on its left border 

 (fig. 127 sg). The seminal receptacle is relatively large, oval, and lies 

 on the caudal borders of the ovary and the posterior testis. The vitelline 

 gland is on the antero-lateral border of the ovary and consists of 6 or 

 more rounded lobes somewhat indistinctly divided into two main masses. 

 A cluster of nucleated cells lies in front of the vitelline glands between 

 them and the ventral sucker, and a large number of similar cells fill the 

 neck. These I take to be yolk-forming cells. The ova are abundant and 

 fill all the posterior parts of the body not occupied by the other organs 

 from the ventral sucker to the posterior end. 



Host, Teuthis ccBTuleus: July 6, 1908, i fish, 2 distomes. 



Dimensions, life: Length 1.89; breadth 0.53; oral sucker 0.08;. 

 pharynx 0.04; ventral sucker 0.32; ova 0.024 by 0.015. 



