65] LIFE HISTORY OF TREMA TODES—FA UST 65 



lateral trunks. These tubes lie just within the margins of the larva and unite 

 with one another in a large transverse vessel at the anterior end of the body, 

 so that a complete circuit is formed. If a rent is produced in the body near 

 the oral sucker, it is customary for the excretory granules to be poured out 

 there rather than thru the natural channel. A tube from the lateral trunks 

 crosses thru the ventral pocket wall at its anterior end. Tributary tubules, 

 bisymmetrically arranged, empty into the main trunks, mostly at the anterior 

 and posterior margins of the body. 



The digestive tract is simple and inconspicuous. A small swelling within 

 the oral sucker marks the pharynx, just behind which is the esophagus. The 

 ceca barely clasp the anterior margin of the primitive genital pore. 



The genital organs are readily recognized as holostome in type (Fig. 47). 

 They open posteriad. A small spherical ovary lies median. Dorsal to this 

 is the ootype, into which come the short oviduct and the transverse vitelline 

 ducts. The vitellaria are diffuse bands of large follicles extending from the 

 anterior face of the acetabulum to the posterior margin of the genital pouch. 

 They lie strictly ventral. Two large oval testes lie to the sides of the ovary, 

 the one (ti) slightly anterior to the other (t,). They have individual ducts 

 (efferent) which reach the genital pouch and fuse into a common vas deferens 

 just before entering the genital pouch. This organ is muscular, oval in con- 

 tour, with the transverse diameter longer than the longitudinal. 



A survey of the literature shows that only one tetracotyle has been re- 

 ported for Amphibia, Tetracotyle crystallina (Rud.), from the mesentery cysts 

 in Rana temporaria, R. esculanta, Bufo igneus, B. viridis, and Vipera berus 

 (Rudolphi, 1819:380-382). The formation of the cysts is not clearly de- 

 scribed, but the large size of the Europen tetracotyle, together with its oval 

 contour, aspinose body and oval accessory sucking discs, clearly separates it 

 from Tetracotyle pipientis. The new species conforms much more to the type 

 represented by T. cohibri v. Linstow, but differs from it in the relative sizes 

 of the oral and ventral suckers, and the possession of small spines all over 

 the body instead of a few broad spines (Linstow, 1877:192; Fig. 22). 



While the excretory system is one of the best systems of organs to use in 

 systematic work with trematode larvae, in the absence of such data for other 

 tetracotyles. described, the comparative data actually afforded are sufficient 

 in this case to justify the establishment of Tetracotyle pipientis as a distinct 

 species. 



Observations on the anatomy of Tetracotyle pipientis present an oppor- 

 tunity for comparison with Cercaria flabelliformis, the parasite of the Bitter 

 Root moUusk, Physa gyrina. 



The two larvae are about equal in length, but C. flabelliformis is consider- 

 ably the wider. The widest region in T. pipientis is in the anterior region of 

 the body; the widest portion of C . flabelliformis is in the middle of the body. 

 The suctorial pocket in the former species has grown over the ventral sur- 

 face so that a true pocket is formed with the opening anterior; in the latter 



