n\ T. HAIUEY .JOHNSTON. (v) 



staining, and situated in the wider part of the gland-cell. These 

 cells were al)()ut 0009 nun. in length, and were especially evident 

 on that part of the vaginal wall immediately before it passes 

 over into the thin-walled receptaculum seminis. 



No bristling of the inner surface of the vaginal wall was 

 recognised. 



'o 



It may not be out of place to give a brief account of the order 

 of development of the genitalia. The genital rudiments ("anla- 

 gen " of many authors) were just recognisable as a small 

 medianly-situated, more deeply staining area, a very short dis- 

 tance behind the region where segmentation became recognisable 

 laterally, that is, at about 01 nnn. from the anterior end. At 

 2 nnn. distance, the " spot " had lengthened somewhat, and the 

 posterior end of it had become subdivided to form the rudiments 

 of the testes, tlie anterior part .still remaining undifierentiated. 

 Further back, a transverst^ly placed " streak " was seen to arise 

 from the latter portion, and to develop laterally for a short 

 distance. At this time the anterior portion had the appearance 

 of being rather obliquely placed, whilst the testes were now small 

 and numerous, but well defined, and occupied a compact zone in 

 the middle of the hinder third of the segment. At 5 mm. from 

 the scolex, the anterior mass was seen as a dense deeply-staining 

 structure, rather sharply marked off from the ^estes. The lateral 

 projection had now developed sufficiently to be seen under the 

 excretory vessel, and shortly afterwards became differentiated 

 more or less completely into the two genital ducts, the more 

 anterior being the vas deferens. Lumina could now be detected. 

 The anterior portion of the genital rudiment was now recognis- 

 able as the slightly coiled precursoi' of the much coiled portion of 

 the male duct. This was traceable backwards along the middle 

 of the segment, where it came into relation with the testes. The 

 outer end of the lateral portion now became swollen and some- 

 what fusiform, this being destined to develop into the cirrus-sac. 

 The ovary and vitelline glands developed later, and more slowly. 

 The male glands had reached their full size, while the female 

 glands wex^e still small. Ne\'ertheless, the latter had practically 



