1911] Watson: The Genus Gyrocotyle. 401 



ture. The cells of the gland are embedded in the innermost of 

 these muscle-bundles. The lumen of the ejaculatory duct is 

 lined with a thin cuticula, beneath which are found cuticular 

 muscle fibres and subcuticular cells. Outside this layer is a 

 thick mass of circular muscle fibres, and outside these a heavy 

 longitudinal layer of fibres. To this coat are attached the 

 radially arranged muscle fibres above described", inserting in 

 general at the angle shown in figure 65, plate 43. 



Spermato genesis. The follicles of the testes are lined by a 

 syncytium in which are embedded rather small rounded nuclei 

 of the spermatogonia. The middle of the follicle is filled with 

 dividing cells and developing spermatozoa. No attempt has been 

 ?nade to work out the details of the process of spermatogenesis. 

 It may be mentioned that in none of the preparations observed 

 by the writer were there any indications of amitosis, but several 

 mitotic figures were observed. The mature spermatozoon is a 

 slender thread tapering at the posterior end, with a well-marked 

 head, several times the diameter of the body and staining in- 

 tensely (pi. 41, fig. 50). 



The Ovum and Oogenesis. Unfortunately the writer has seen 

 no young specimens of Gyrocotyle. While there has been great 

 variation in size, in all individuals the uterus has been full of 

 developing embryos which mark the specimens as sexually 

 mature. Lonnberg, the only investigator who has had the good 

 fortune to work with the immature form, described the ovaries 

 in the young individuals as follows : 



"Das Ovarium hat bei jiingeren Individuen eine nicht gewohnliche 

 Gestalt, indem es viel mehr traubig gelappt als bei anderen Cestoden 1st. 

 Es besteht also in diesem Stadien aus kleinen rundlichen Follikeln, die 

 durch weite Ausfuhrungsgange zu Trauben vereinigt werden, und diese 

 Trauben erster Ordnung werden durch ihre Ausfiihrungsgange zu Trauben 

 zweiter Ordnung verbunden. Alle Trauben vereinigen sich zu je einer 

 Sammlung aufschmelzen aber allmalig die Trauben zu unregelmassigen 

 Lappen zusammen und es seheint daher nicht treffend, wenn Spencer auf 

 seiner schematischen Figur ein so distinkt traubenfb'rmiges Ovarium bei 

 einem Tiere mit von Eiern prall gefiillten Uterus zeichnet. " 



Spencer (1889, p. 144) dealt with sexually mature forms, but 

 found two stages of reproductive activity : 



"In the first-mentioned the ova were evidently passing down into the 

 uterus, in which they were but very slightly developed. The ovaries 



