104 NEW GYEODACTYLOID TEEMATODBS FROM AUSTRALIAN FISHES, 



of the sperms from the testis, appears as a large flattened structure, somewhat 

 lobed at its edges, occupying the greater part of the dorso-medial region of the 

 body from immediately behind the phai-ynx to the ovary. The whole structure 

 is filled with spenns floating in an albuminous material. The prostate glands 

 have now increased greatly in size. The bulbus ejaculatorius has enlarged con- 

 siderably and communicates with the seminal vesicle by a plainly-visible duet. 

 The cirrus has grown greatly in size and complexity and has developed a flange 

 which travels along one side of it for about two-thirds of the leng-th of the 

 organ, and then suddenly passes over to the oth«r side and ceases abruptly. 

 This portion of the cirrus runs horizontally, but thence onward it slopes down- 

 ward and gradually develops another flange which continues almost to the 

 genital opening. The whole structure is enclosed in the lai'ge cirrus-sac (Pi. 

 xvi., fig. 39). 



The female organs do not mature at so early a stage as do the male. The 

 ovary lies immediately anterior to the testis and on its right side gives off an 

 extension. The oviduct is a narrow tube arising from the median ventral sur-. 

 face of the ovary and travelling foi-ward near the ventral surface of the animal. 

 The extremely large vagina opens on the left ventral side on a level with the 

 prostate glands. A receptaculum seminis is absent. The female genital open- 

 ing is situated a little behind the male aperture. The oviduct and uterus are 

 extremely thin-walled structures. The shell-glands (PL xvii., fig. 49) consist 

 of large masses of glandular cells, situated around and opening into the ootype, 

 but visible only in sections. Never more than one egg is present in the uterus 

 at a time. The egg, which measures .07 mm. by .048 mm., is provided with 

 a short posteriorly-directed spine. The nucleus is visible among the abundant 

 granular yolk material. 



The vitellaria are well developed and arranged in two broad bands, one 

 on either side of the body, almost entirely obscuring the intestine. Posteriorly, 

 immediately behind the testis, the yolk accumulates in a large median mass. 

 In adults the organs may extend anteriorly to the pharynx and there is also a 

 slight development of them all along the dorsal surface posterior to this organ. 



The individual parasites do not appear to have much effect on the host, 

 though a slight hypertrophy of the gill-tissue has been observed in a few 

 cases. But the great numbers in which this parasite occurs on the gills, must 

 render it a source of considerable irritation to its host, as many as twelve 

 individuals having been counted on a single gill-filament. 



Found on the gills of Therapon carbo Ogilby and MeCulloch, from the 

 Thomson River, Longreaeh, Central Queensland. 



Lepidotrema tenue, n.sp. (Plate xvi., fig. 43; xviii., tigs. 52, 53.) 



Length .69 mm. by .14 mm. This species closely resembles L. therapon 

 both anatomically and in general appeai-ance, but the majority of the specimens 

 examined were considerably longer and more slender. The clasping disc is very 

 similar in the two species, the large hooks, chitin bars and scaly "discs" being 

 indistinguishable, but the disposition of the minor hooks is diffei-ent, as is seen 

 bv comparing figaires ¥3 and 42 (Fl. xvi.). A very short oesophagus is deve- 

 loped and there is no fusion of the intestinal limbs posteriorly. The most marked 

 differences are visible in the reproductive organs. As in Lepidotr.emm therapon, 

 t'lie testis matures in quite young forms. Degeneration of this organ occurs as 

 in that species, though it is not so complete, a testis containing developing 

 sperms being plainly visible in even the largest forms. Corresponding with this 



