108 NE1V GTRODACTYLOID TEEJIATODES FROM AUSTRALIAN PISHES, 



walls. There is no definite oesopbagiis. The intestine is devoid of caeca and 

 the two limbs bulge outwards in the region of the testis and end blindly. There 

 are two glands situated one on either side of, and immediately posterior to, the 

 pharynx; they seem to open into the intestine. 



There are four pairs of head-organs from which the ducts pass backward 

 to join the cephalic glands. In young forms the head-organs are all clustered 

 closely together ; but already in medium-sized forms the adult condition ' is 

 attained (PL xx., fig. 70). 



Of the nervous system, only the brain and the origin of the main nerves 

 could be recgg-nised. There are two pairs of eyes, each consisting of a mass of 

 minute oval pigment-gxains, lying well -ndthin the body-parenchyma. 



The sexual apparatus is very complex and difficult to follow out. The 

 following description is based on an examination of whole mounts and seiial 

 sections. 



The testis is extremely large, oeeuiDying all the space between the brandies 

 of the intestine. Within the testis the immature sperms are arranged in 

 numerous small clusters, but further details of sperm formation could not be 

 observed in this organ. The vas deferens is a wide tube, passing forward and 

 opening immediately behind the pharynx into a portion of the vesieula seminalis. 

 The latter consists of three large globular portions. The anterior, dorsally 

 situated part appears to open by a duct given ofi from its lower surface intp 

 the ventral portion of a second division lying immediately behind it and like- 

 wise dorsally. This opens, in turn, into a third, more ventrally situated portion 

 which appears to open directly into the large bulbus ejaculatorius. Tliis lattei 

 is a thick-walled vesicle which opens by a narrow duet into the cirrus. Sperms 

 appear to undergo' development in the vesieula, for not until they are found in 

 the ejaculatory bulb do they possess a typical sperm-appeai-ance. The heads 

 are minute and spherical, the tail relatively long, the whole sperm measuring 

 about .008 mm. The cirrus, which lies in a large cirrus-sac, is a rather simple 

 cljitinous tube, bent once upon itself. Into the cirrus also open, by a pair of 

 long ducts, two prostate ( ? ) glands and also a large number of very prominent 

 heavily-staining glands ("cirrus glands"), originating as far back as the ovary. 



The prominent ovary is situated asymmetrically in front of the testis, on 

 the right side of the body. Into the narrow oviduct opens a large yolk reservoir, 

 generally difSeult to see, since it seldom contains yolk. The vagina is a simple 

 tube passing directly to the left side where it opens ventrally. In connection 

 with it there is a large receptaculiun seminis, frequently seen full of sperms. In 

 whole specimens it is almost completely obscured on account of the great develop- 

 ment of the vitellaria. 



The oviduct passes forward as a very thin tube opening close behind the male 

 aperture. Distinct shell-glands could not be recognised but these organs seem 

 to be represented by certain glandular swelling's in the walls of the ootype. The 

 large, oval egg, measuring .07 mm. l)y .04 mm., is well supplied with yolk. 

 Posteriorly it bears a small blunt spine. Of fifty specimens examined only two 

 contained an egg. 



The vitelline system is fairly well developed. Two wide transverse yolk-duots 

 are present immediately behind the ovary and transfer the yolk to a reservoir 

 which is generally very diflBeult to detect, exeejat when filled. 



In general appearance the young differ considerably from the adults. In 

 the smallest forms the head-organs are ehistered closely together. Testis and 

 ovary are small. Vesieula seminalis, bulbus ejaculatorius and cirrus are ^nsible; 



