646 L. R. Cary. 



The cj^stogenous glands. 



The cystogenous glands arise at a comparatively late stage in 

 the development of the embryo, through a transformation of the 

 meristem cells in an area along either side of the body. These 

 cells increase greatly in size and their contents become highly gra- 

 nular, while their cytoplasm becomes restricted to the interstices 

 between the granules of the secretion. 



The c u t i c u 1 a. 



The origin and nature of the cuticular covering of trematodes 

 has been one of the most discussed questions concerning their histo- 

 logy. The opinion which has received the most support among 

 modern investigators, is that the covering is a true cuticle, i. e. the 

 product of an epidermis. The epidermis is believed to be represented 

 by deeplying glandular cells, whose ducts traverse the muscular 

 layers and the basement membrane to pour their secretion on the 

 outer surface of the latter. According to some observers, the ori- 

 ginal covering of the embryo (the investiug membrane), goes to make 

 up the basement membrane of the adult worm. 



In sections through j^oung embryos before the cuticula has been 

 formed, there are found near the outside of the body a considei'able 

 number of large cells with deeply staining contents. In favorable 

 sections the mouths of these cells can be traced through the 

 outer tissues to the basement membrane. After the cuticula has 

 been formed the above mentioned cells are very different in ap- 

 pearence. They no longer stain deeply with haematoxjdin, while the 

 newly formed cuticula has the same staining reaction that was 

 shown by the contents of these cells before the cuticula had been 

 formed. 



The evidence gathered in the study of the formation of the 

 cuticle in this species confirms the view as to the true cuticular 

 nature of the outer body covering as first set forth by Blochmann 

 and KowALEvsKi. 



The body p a r e n c h y m a. 



The body parenchyma cells arise by a direct transformation of 

 the meristem cells of the embryo. The cytoplasm of these cells, 

 which in the young cercaria forms a continuous mass, in which the 

 nuclei are imbedded, later becomes broken up into branches which 



