80 Papers from the Marine Biological Laboratory at Tortugas. 



Gasterostomum sp. (Figs. 217, 217a, 218.) 



Body linear, truncate, or capitate anteriorly, bluntly rounded pos- 

 teriorly, covered with very minute spines; anterior sucker large, terminal, 

 with conical base ; genital sucker a little in front of the middle of body ; 

 esophagus short, intestine ovate. Testes 2, 1 behind genital sucker 

 and close to it, the other a little farther caudad, nearly as far back as 

 the anterior end of the cirrus-pouch; both nearly on the median line, the 

 anterior the larger. The cirrus-pouch lies along the left side, ample, 

 with small pyriform seminal vesicle inclosed in the anterior end (fig. 

 21857;) and the prostate throughout its length. Ovary small, situated 

 at the right of the genital sucker and a little caudad. Vitelline glands 

 lateral, from level of genital sucker, or a little in front of it, in an irregular 

 row, sixteen, more or less, globular bodies in each row. The folds of the 

 uterus extend from the anterior testis to the posterior end. The ova are 

 elliptical with rather thick shells. This description is based on the 

 specimen sketched (fig. 217). There is considerable variation in the rela- 

 tive position of the testes and ovary. 



This species bears some resemblance to G. baculum Linton. 



Host, Mycteroperca venenosa: 



1907, July 14, 1 fish, few trematodes. 



1908, June 27, 1 fish, 10 trematodes. 



Dimensions, in life, flattened: Length 0.95; breadth 0.21; anterior 

 sucker 0.14; ventral sucker 0.04; ova 0.030 by 0.020. Dimensions of 

 another, in balsam: Length 1.20; breadth 0.24; anterior sucker 0.15; 

 ventral sucker 0.05; ova 0.03 by 0.02; distance from anterior end to 

 ventral sucker 0.56. 



Gasterostomum sp. (Figs. 223-225.) 



Brief mention is here made of finds of this genus in the barracuda. 

 Like all the representatives of this genus found by me at the Tortugas, 

 they are in poor condition and it is impossible to make out details of the 

 anatomy satisfactorily. It does not seem credible that such diverse 

 forms as those shown in figs. 223, 224, and 225, can belong to the same 

 species. Figure 225 was sketched from life, but neither it nor any speci- 

 men exactly like it appears among my stained and mounted material. 

 Aside from this there is still a perplexing variety in the material collected 

 from the barracuda. 



In general these forms are characterized by having the anterior 

 end elongated in front of the vitelline glands, with a rather small, but 

 apparently anterior, sucker. Both fusiform and linear forms occur. 

 The body is covered with exceedingly minute spines. A striking differ- 

 ence is found, among forms otherwise in close agreement, in the character 

 of the ova. Indeed there seems to be greater diversity in the shape of 

 the ova in the same species and even in the same individual in this genus 

 than prevails among the distomes. 



These specimens agree in having the vitellaria lateral to the genital 

 sucker and in having the testes behind the genital sucker. Also the 

 ovarv is in front of the testes and on the right side in all. The testes 

 do not agree either in relative size or in position. In fig. 223 they are 



