AST. 1 TREMATODE PARASITES OF BIRDS LINTON 31 



of the posterior division of the body, one following the other, but 

 separated by a space in which lie the transverse yolk reservoir, the 

 shell gland and ootype, and the beginning of the uterus. The ovary 

 is situated close to the anterior border of the first testis. As seen 

 in lateral view it is long-oval, the transverse diameter greater than 

 the longitudinal, tapering at the median end, thus becoming some- 

 what pyriform. In a specimen from the laughing gull, mounted 

 in balsam, the longer diameter is 0.28, shorter diameter 0.15. The 

 first testis in this specimen had a maximum breadth of 0.45 and 

 length of 0.24; second testis, breadth 0.59, length 0.36; distance of 

 second testis from posterior end 1.40, or approximately one-fourth 

 the entire length. In whole mounts of specimens from the ring- 

 billed gull the ovary had the same dimensions as those given above: 

 first testis, length 0.56, breadth O.TO; second testis, length 0.49, 

 breadth 0.70; distance of second testis from posterior end approxi- 

 mately one-fifth the entire length in each. Behind the second testis 

 there is a capacious seminal vesicle and a contorted, thick-walled 

 ejaculatory duct. The copulatory bursa was invaginated in all cases. 

 It is fairly well developed, as shown in Figure 71, which is some- 

 what diagrammatic, and occupies about one-half the distance between 

 the second testis and the posterior end. The vitellaria are dis- 

 tributed mainly on the ventral side from near the constriction be- 

 tween the two divisions of the body to near the posterior end. In 

 the specimens from the ring-billed gull and herring gull they were 

 strongly developed, so much so as to mask much of the anatomy. 

 The yolk reservoir is tubular. It originates on the ventral side and 

 lies along the anterior border of the second testis. There is much 

 variation in the number of ova. For example, in the specimen from 

 the laughing gull there are relatively few ova, about 29, while two 

 from the ring-billed gull contain the one 133 and the other 220, and 

 one from the herring gull contains about 375. In one of the three 

 series of sections the ova are few, in the others there are many. 

 There is not much difierence in the size of ova in the different ex- 

 amples. In the balsam mounts they do not vary much from 0.11 

 by 0.07 in the two principal diameters. The course followed by the 

 uterus is in all cases from its origin between the testes forward towards 

 the anterior end of the posterior division of the body, whence it 

 returns on the ventral side to the posterior end. There is no seminal 

 receptacle, but the early folds of the uterus were seen, in some of the 

 series of sections, to be filled with sperm. In one series of sections 

 the germ duct throughout its somewhat tortuous course, from near 

 the ovary to the shell gland, as well as the earlier folds of the uterus, 

 was filled with sperm. 



Laurer's canal opens on the dorsal surface about on a level with 

 the anterior border of the first testis. It is a small, somewhat con- 



