71] LIFE HISTORY OF TREMATODES— FAUST 71 



66). Ovary, Laurer's canal, vagina, uterus — all are recognized in the midace- 

 tabular region, with vitelline follicles extending from the oral aperture to the 

 posterior end. They are divided into anterior and posterior portions. No 

 testes are yet to be found. The genital organs as a whole seem to indicate 

 Plagiorchid relationship. 



Conspicuous thruout the body are the large bundles of longitudinal muscle 

 fibers. They are scattered thruout the parenchyma at the anterior end 

 (Fig. 72), while they are much larger and more concentrated laterad in the 

 region of the acetabulum. Still further caudad they become fewer and less 

 conspicuous (Fig. 74). 



The nervous system has been described in detail on page 51. 



This cercaria lives a free-swimming existence for only a short time. When 

 placed in a watch-glass in tap water, it soon drops its tail, preparatory to 

 encystment. The tail is helpful in locomotion, yet after decaudation this 

 species is more active and able to cover considerably more ground than most 

 other species v/ith the aid of the tail. This movement is due in no small 

 measure to the spines in the locomotor grooves of the caudal pockets. After 

 moving about for a little while the cercaria settles down and pours out an 

 abundance of shme within which it coils up and becomes quiescent until a 

 transfer to the new host is effected. 



Cercaria diaphana Faust 1917 



Cerceria diaphana is closely related to C glandulosa. When contracted, 

 it is broadly ovate (Fig. 78), but on extension it assumes an elongate ovoid 

 contour (Fig. 76). The measurement of the body when at rest is 0.2 mm. to 

 0.26 mm. in length by 0.1 mm. to 0.12 mm. in width. Under pressure of a 

 cover slip the internal organs are beautifully worked out and the delicate 

 mist of the parenchyma in which they are imbedded suggests the term "dia- 

 phanous. " The tail is broadly lanceolate, 0.15 mm. in length by 0.04 mm. at 

 the base. It is inserted into a caudal pocket provided with spinose locomotor 

 pocket grooves. The spines are few in number (8 to 10) and well developed. 

 They are directed meso-caudad. As in C. glandulosa the two sinuses of the 

 caudal pocket are thickened by a mucoid lamination. The acetabulum is 

 situated in the middle of the ventral side; it has a diameter of about 32/i. The 

 larger and more powerful oral sucker has a diameter of 44/i. The stylet organ 

 (Fig. 77) is a delicate but firm quill of 39/i length and Sn width at the base 

 of the shank. It is entirely without any reinforcement in the region of the 

 shank but has thin ventral plates at the junction of the shank and quill, while 

 inserted in the quill point, directed posteriad, is a minute spine, 5/* long and 

 0.5^1 in diameter. 



Cercaria diaphana was found in the liver tissues of Lymnaea proxima in 

 the Bitter Root River near CorvaUis in October 1916. The infection was 

 heavy. The cercaria develops in an oblong sporocyst (Fig. 79), frequently 

 drawn out or contorted at one end (Fig. 80). The unique feature of the 



