44 ILLINIOS BIOLOGICAL MONOGRAPHS [44 



The redia has a gut-pouch for a digestive system, with a pharynx sphincter 

 around the anterior end. Hence the epidermis is not used in the capacity 

 of food transference, and is heavily Kned beneath with an integvmientary 

 secretion. For securing food the redia of Cercaria pdlticida is provided with 

 an oral piercing organ. The redia of C. flabelliformis is equipped with paired 

 mucin-salivary glands. 



GENITAL SYSTEM 



This system of organs has been the most constant basis of classification 

 of adult trematodes. It is also the best specific criterion for the larvae, altho 

 a more deUcate technic is required for differentiation of the genital organs in the 

 cercaria than in the adult worm. Because these organs have failed to come 

 out in the ordinar>^ preparations, no attempts have been made to use them as 

 basis for correlating larvae and adults. Cell masses have been figured by Looss 

 (1896), Ssinitzin (1905, 1911) Miyairi and Suzuki (1914) and Cort (1915), but 

 these workers have not in any case showTi them in detail. By means of a 

 lengthy staining in a weak solution of Delafield's hematoxylin, followed by 

 rapid differentiation and then neutralization with potassium acetate solutions 

 in the higher alcohols, the genital organs of the cercariae have been traced 

 with a degree of detail not previously attained. These organs have been found 

 to offer valuable data for correlating cercariae and adult trematodes. 



A. Monostomata. All three species of monostomes on which observations 

 have been made, Cercaria pellucida, C. kanadensis, and C. urbanensis Cort are 

 characterized by the symmetrically arranged testes, the presence of Laurer's 

 canal, the location of the vitelline glands in a double series on each side of the 

 body, and the courses of the uterus and vas deferens. Ssinitzin (1905, Fig. 

 76) shows the inner series of five paired vitellaria for C. ephemera Nitzsch, but 

 he has figured no outer series of three glands, such as are found in the three 

 species worked out by the \NTiter. He is in error in considering them cj'sto- 

 genous glands, because their connection is traceable thru filiform ducts to the 

 ootype. All these species are provisionally referred to the Notocotyhdae. 

 With the growth of the cercaria to the adult monostome the originally distinct 

 and readily recognizable vitelline elements becomed fused in part. Looss 's 

 figure (1896, Fig. 94) of Notocotyle verrticosa (Froel.) shows five rather poorly 

 defined foci of vitelline elements in each of the lateral series. It is possible 

 that the five inner elements of the series have become fused to the three outer 

 elements of the series, thus causing the indefinite outline of the elements in 

 the adult worm. The vitelline glands of Notocotyle quinqueseriale are ap- 

 parently eight to the side. Here the three glands of the outer series may have 

 been introduced between the five glands of the inner series (Barker and Laugh- 

 lin, 1911, PI. 1, Fig. 10). A symmetrical pair of \dtelline ducts, between the 

 inner and outer series of glands, leads to the ootype. 



The cercariae which the writer has studied in this group are readily dis- 

 tinguished by a comparison of their genital systems. 



