30 ILLINOIS BIOLOGICAL MONOGRAPHS [248 



gives rise to a relatively large cylindrical unarmed ductus ejaculatorius. 

 In most individuals the ductus ejaculatorius and pars prostatica are much 

 coiled inside the cirrus sac and can be made out only with considerable 

 difficulty. The writer has had the good fortune to have for study two 

 specimens of Cyclocoelum brazilianutn Stoss. one of which has the ductus 

 ejaculatorius protruded from the body. The other one with the ductus 

 ejaculatorius extended into the uterus in a case of evident self-copulation. 

 (Figs. 31, 35). In these specimens the ductus is in excellent position for 

 study and appears as described above. Through the union of the end 

 portion of the cirrus pouch and the uterus a relatively large genital atrium 

 is formed. 



The form of the genital glands throughout the family is in general very 

 similar. They are usually round or elliptical, sometimes flattened from 

 pressure of the surrounding parts, with the exception of Cyclocoelum vicar- 

 iutn (Arned.) and in the genus Typhlocoelum in which species the testes 

 are lobed. The genital glands of the genus Cyclocoelum, the only Amer- 

 ican genus thus far known belonging to this family, are spherical in form. 

 The testes are located so the posterior is in or near the posterior intes- 

 tinal arch and the anterior, a greater or less distance from this, separated 

 often by uterus loops. Exceptions to this are found, however, in Cyclo- 

 coelum oculobium (Cohn) and Bothriogaster variolaris Fuhrmann in which 

 the ovary occupies the posterior intestinal arch while the testes are situ- 

 ated in the middle region of the body. The vasa efferentia given off from 

 the testes unite a short distance anterior and median to the anterior 

 testis in Cyclocoelum obscurum, to form the vas deferens which makes its 

 way between the uterine loops to the cirrus pouch previously described. 

 The ovary is spherical and communicates by a short duct to the compact 

 closely lying shell gland. 



The presence of the receptaculum seminis and Laurer's canal have been 

 held in question since the earliest accurate work on the anatomy of these 

 worms, that of von Siebold (1835) who described in Monostomum mutabile 

 as organs contributing to the formation of the egg four distinct glands, the 

 vitellaria, which he interpreted as the ovary as follows: — "Die Ovarien 

 bilden kurze blinde Schlauche, die unter einander anastomosiren und den 

 Darmkanal, nachdem er vom Oesophagus aus die Seitenrander des Leibes 

 erreicht hat, in seinem ganzen weiteren Verlaufe wie ein Netz umgeben. 

 Es ist dies eine eigenthumliche Anordnung, die ich bis jetzt noch bei keinem 

 anderen, zu den Trematoden gehorigen Wurme angetroffen habe." The 

 three other parts having to do with the formation of the shell are de- 

 scribed by the following characteristic statements: — "An der zweiten 

 Abtheilung der weiblichen Geschlechtstheile, die zur Bildung der Eier- 

 haute bestimmt zu sein scheint, lassen sich deutlich drei eigenthumliche 

 Organe erkennen. a) Erstens fallt hier ein runder, weissgelber Korper 



