1904.] DISCOVERED TURBELLARIAN WORM. 409 



Reproductive System (Plate XXY. figs. 6, 7). 



A. incola is hermaphrodite and is found sexually mature at 

 Millport, N.B., in June and July. 



The penis is situated on the ventral surface at the junction of 

 the posterior fourth with the rest of the body. It is conical and 

 carries a knob-like ai-mature at its distal end. At its proximal 

 end its duct dilates to form a pyriform vesicula seminalis, the 

 walls of which are formed by a thickening of the surrounding 

 dermal parenchym and into which the testes open on either side 

 by no distinct or epithelially lined channels. The testes consist 

 of follicular masses extending forwards on either side in the 

 parenchym of the lateral parts of the body, outside the ovaries, to 

 beyond the mouth, and posteriorly also for a short distance into 

 the tail. The sperm-follicles near the vesicula seminalis contain 

 deeply staining chromatin figures. 



The ovaries extend on either side of the middle line from 

 beneath the brain to within a short distance of the male apparatus. 

 They early unite, but are soon separated by the digestive vacuole, 

 joining again in the posterior middle fourth of the body (figs. 1, 2). 

 The ova increase in size as they pass backwards and ai-e enclosed 

 in delicate parenchyma, each occupying latterly a sepai-ate " follicle." 



No accessory female organs are present. Thei-e is no vagina 

 through which the ova can be extruded, and it would appear from 

 a careful examination of ripe specimens that the cuticle simply 

 gives way before the ripe ovum owing to an ever-increasing growth- 

 pressure — this rupture taking place at a short distance in front 

 of the penis (fig. 7). In several examples the ova lying most 

 posteriorly had acquired a relatively dense capsule, stainable with 

 osmic acid, and these not infrequently showed mitotic figures. 

 These facts, taken in relation with the armature of the penis, seem 

 to point to copulation being effected by simple perforation of the 

 cuticle. 



Systematic Position. 



The turbellarian now described dijBfers along with all the species 

 of Haplodiscus from other Acoela in that it possesses no female 

 accessoria. From Haplodiscus also it difiers in the following 

 respects : — 



(1) Shape. 



(2) Parasitic habitat. 



(3) Mouth in anterior fourth, 



(4) Paired lateral testes. 



(5) No defined vasa deferentia. 



(6) Penis with knob-like armature. 



(7) Frontal organ well developed and opening by many 



mouths. 



(8) Large digestive vacuole. 



These diflferences seem to be of sufficient importance to wairanfe 

 the erection of a new genus, which I have called Avagina. As an 



