OF A TETRACOTYLIFORM LARVA TO A HOLOSTOMUM SP. 391 



been able to trace their efferent ducts to the vesicula seminalis 

 (Fig. 10, v.s.) This is a long swollen sinuous duct, the basal 

 end of which is semi-pyriform ; and as it runs upwards along the 

 ventral border carrying the spermatozoa, it gradually becomes 

 thinner and finally makes a junction with the pore and dis- 

 charges the sperm into the laurer canal, thus filling the recepta- 

 culum seminis (Fig 10). 



Thus it will be seen that in this species, as in von Linstow's 

 Ilolostomum excisum, no male organ of copulation (cirrus) exists, 

 and in this respect this Trematode is analogous to, and has an 

 affinity with, Hymenolepis acicula sinuata. 



In this species of Ilolostomum there is no side cavity or cleft 

 as in H. excisum, but the cavity exists as a cup whose peristome, 

 in its early stage, is subspherical (Figs. 1-4). As development 

 proceeds, however, the periphery becomes crenate, and in the 

 perfected or sexually mature creature we have a distinctly 

 crenate calyx, or cup. The genital papilla at the posterior or 

 caudal end is not protruded until the genital organs are matured. 

 It is capable of evertion and invertion, and I am in accord with 

 von Linstow in believing that its function is that of a uterus 

 cylinder for the deposition of the ova. Dujardin, Hist, des 

 Helminth., p. 372, No. 10, somewhat dubiously refers to Rudolphi's 

 statement of his having seen in Amphistoma {Ilolostomum) cornuta 

 such a phenomenon, viz. the evertion of the " Corne " and depo- 

 sition of the ova, and its retraction after the act. Fig. 15 is 

 from a specimen in my cabinet in which the creature is seen in 

 the act of depositing the ova through this cylinder. 



Description of Plate 29. 



Fig. 1. This has been reconstructed, and as seen in the 

 mounted specimens would raise a doubt in the investi- 

 gator's mind as to its being the primary stage of the 

 released embryo, but of this I have no doubt. In 

 passing it through the various grades of dilute 

 glycerine to its final mounting-medium, pure glycerine, 

 it became unfortunately mutilated. The primitive 

 mouth-sucker is plainly visible. x 45. 



Fig. 2. This coincides with Fig. 1 of von Linstow's young 

 form of Tetracotyla typica (Fig. 17). x.45. 



