300 WILLIAM A. HASWELL. 



which the ejaculatory duct and the vagina open ; there are two 

 pairs of lobed testes, vitelline glands, which partake of the 

 imperfect segmentation of the body, a single ovary, recepta- 

 culum seminis, oviduct and uterus. 



The broader questions suggested by the imperfect segmen- 

 tation of Temnocephala, and by other features in its organization 

 which seem to point to a possible genetic relationship with the 

 segmented worms, cannot well be dealt with until the develop- 

 ment has been investigated. 



EXPLANATION OF PLATES XX, XXI, & XXII, 



Illustrating Mr. William A. HaswelPs paper "On Temnoce- 

 phala, an Aberrant Monogenetic Trematode." 



PLATE XX. 



Fig. 1. — Temnocephala fasciata in various positions. Natural size. 



Fig. 2. — Temnocephala fasciata, from living specimens. Magnified. 



Fig. 3. — Temnocephala quadricornis. Magnified. 



Fig. 4. — Temnocephala minor, dorsal view, from preserved specimen. 

 Magnified. 



Fig. 5. — Temnocephala minor, ventral view. g. Genital aperture. 

 m. Mouth. *. Sucker, te. Tentacles. 



Fig. 6. — Diagram of the general organization of Temnocephala. ph. 

 Pharynx, i. Intestine, ex. Excretory sac. ex' . Anterior canal of excretory 

 system, ex" . Posterior canal of excretory system. br. Brain, cl. Genital 

 cloaca. te. Testes. v. d. Vas deferens, p. Penis, re. Receptaculum 

 seminis. ov. Ovary, od. Oviduct and uterus, vit. Vitelline glands, s. 

 Sucker. 



PLATE XXI. 



Fig. 1. — Transverse section through the body wall of Temnocephala 

 fasciata. c. Cuticle, e. Epidermis, b. Basement membrane, c. m. Cir- 

 cularly arranged layer of muscular fibres, p. Pigment layer. /. m. Longi- 

 tudinal layer of fibres, par. Parenchyma. 



