61] LIFE HISTORY OF TREMATODES— FAUST 61 



innervation from the dorsal trunks; the paired eyes are innervated from the 

 posterior trunks and the median eye from the fused branch of the anterior 

 dorsales. The optic nerve runs forward from its origin in the dorsalis and 

 enters the pigment cup from above, ending in a sensory cell (Fig. 24). The 

 general anatomy and histology of this eye-spot is similar to that described for 

 all Turbellaria and Monogenea. However, no previous account has been 

 found for the structure of the eye-spot of the Digenea showing its relation to the 

 central nervous system. 



Locomotion is brought about thru a cooperation of the body musculature 

 together with the special functioning of the oral sucker and the posterior loco- 

 motor pockets. The tail serves as a swimming organ, with a peculiarly rapid 

 and nervous lashing. 



Encystment occurs as a final step in the larval stage of the life-history of 

 the hermaphroditic generation, in preparation for entering the definitive host. 

 The process is rapid and the mucoid cyst is secreted by the cystogenous glands 

 before the tail has been thrown oflf. This organ is freed from the cyst by the 

 violent v/riggHng which it produces. The cyst is spherical ; it encloses the now 

 quiescent larva. The outer portion of the cyst is an opaque mucoid, which 

 gives the cyst an appearance of a white grain, about the size of a pin-head. 

 The larva now waits transfer to the definitive host. 



Cer carta konadensis Faust 1917 



Cercaria konadensis is a species of monostome cercaria of the binoculate 

 type. The species is more graceful than C. pellucida. Its bodily contour 

 is most usually spatulate, while the long tail reaches far behind. The small 

 amount of pigmentation around the two eye-spots and the less usual pigmenta- 

 tion along the nerve trunks caudad serve to indicate the superficial differences 

 between the binoculate group to which this form belongs and the trioculate 

 group. 



Cercaria konadensis was found in Lymnaea proxima Lea, collected from the 

 Bitter Root River at CorvalHs Montana in October 1916. It occurred as an 

 infection along with the larger species, C. pellucida. Of the snails examined, 

 31.3 per cent were infected with this cercaria in the connective tissue be- 

 tween the liver ceca. The cercaria measures 0.4 mm. to 0.46 mm. in length 

 and has a bodily width of 0.1 mm. to 0.16 mm. (Fig. 25). The tail is of equal 

 length under conditions of relaxation, but may be extended so as to exceed 

 by far the bodily length. At its base it has a transverse diameter of 30^i to 

 40)U. The posterior locomotor organs are not so conspicuously lateral as 

 those of C. pellucida (Fig. 4). Considered together with the younger stage 

 of C. pellucida (Fig. 12), these pockets suggest an origin from the caudal 

 pockets found in certain distome cercariae. Unlike those of C. pellucida, the 

 posterior locomotor pockets of C. konadensis are provided with about ten 

 gland cells surrounding the lumen, cells probably of a secretory nature (Fig. 

 21). 



