ACT. 17 PARASITES OF AMPHIBIA AND REPTILIA HARWOOD 27 



in length. The intestinal ceca extend nearly to the posterior end. 

 The ovary is spherical and lies on the midline or just to the left; it 

 is usually anterior to the middle of the body, but its exact relative 

 location is subject to some little variation. This point will be dis- 

 cussed more fully below. The shell gland and ootype lie immedi- 

 ately behind the ovary; and in favorable specimens Laurer's canal 

 may be seen extending directly to the dorsal wall. The uterus 

 extends posterior on the left side and anterior on the right. The 

 metraterm is straight and measures from 0.67 to 0.8 mm long, or 

 very nearly one-half the distance from the genital pore to the ovary. 

 The vitellaria are arranged in lobes between the intestinal ceca and 

 the lateral margins of the body. The follicles are arranged in 

 groups, with 20 to 40 to the group. The most cephalic extent of the 

 vitellaria is about the level of the caudal end of the metraterm. 

 Their length is to the length of the body as 2 : 5. They extend about 

 three-fourths of the total distance from ovary to the anterior testis 

 The eggs vary in size from 34/x, by 17/x to Mfi by 21 fx. The testes are 

 oval and of about equal size. They vary in size from 0.42 by 0.3 to 

 0.2 by 0.12 mm. The caudal testis is removed from the posterior 

 end by a distance greater than its diameter. The cirrus sac is 

 shorter than the distance from the genital pore to the ovary. It is 

 1.5 to 1.2 mm long and contains a seminal vesicle that is 0.36 to 

 0.43 mm long. 



Host. — Pseudemys elegans. 



Habitat. — Intestine. 



Locality. — Houston, Tex. 



Type specimen.— U.^.'^.M. Helm. Coll. No. 30889; additional 

 specimen, No. 30890. 



Remarks. — The position of the ovary in the body has frequently 

 been used as a criterion for separating different species in the genus 

 Gercorchis. A study of my material, which consists of fully mature 

 worms and of barely mature worms, as is shown by their unde- 

 veloped vitelline glands and weakly outlined ovary and testes, has 

 demonstrated that the position of the ovary may vary widely accord- 

 ing to the age of the specimen. In one individual, which is 8.3 mm 

 long and fully mature, the ovary is 3.2 mm from the anterior end. 

 In another individual, 3 mm long but sexually mature as shown by 

 the presence of eggs in the uterus, the ovary is 1.5 mm from the 

 anterior end. From analogy with the nematodes this variation 

 might be expected. In these worms it has been found that the 

 anterior region of the worm changes but little after reaching sexual 

 maturity, while the posterior end may enlarge considerably on ac- 

 count of the pressure of the enormous number of eggs. So it might 

 be expected that the posterior region of a Cercorchis worm would 



