158 



COLLEGE ZOOLOGY 



thin, hard covering often called the cuticle; it protects the under- 

 lying tissues from the juices of the host. The ectoderm contains 



chitinous scales and unicellular 

 glands. The entoderm lines the 

 alimentary tract. The mesoderm 

 is represented by the muscles, 

 the excretory organs, the repro- 

 ductive ducts, and the paren- 

 chyma. The parenchyma is a 

 loose tissue lying between the 

 body-wall and the alimentary 

 canal ; within it are embedded 

 the various internal organs de- 

 scribed above, as well as the 

 reproductive system. 



Both male and female reproduc- 

 tive organs are present in every 

 adult; they are extremely well 

 developed, and, as in Planaria, 

 quite complex. Those of the 

 male are as follows: (i) a pair of 

 branched testes (Fig. 105, T) in 

 which the spermatozoa arise ; 

 (2) two ducts, the vasa deferentia, 

 which carry the spermatozoa from 

 the testes to (3) a pear-shaped 



FIG. 105. -e liver fluke, Fas- SaC > the seminal side >' 

 ciola hepatica. D, anterior part of voluted tube, the ejaculatory duct, 



which leads to the end of a 



O, mouth; Of, uterus; s, sucker; muscular copulatory organ, the 



T, testes. (From Sedgwick, after ,,,. 

 Sommer.) P emS ' 



The female organs are (i) a 



single-branched ovary (Fig. 105, Dr) in which the eggs are 

 produced; (2) a convoluted oviduct (Fig. 105, Ov) which trans- 

 ports the eggs from the ovary to (3) the shell gland, at which 



