I2 DISCOVERY REPORTS 



The heart lies well forward in front of a marked pericardio-peritoneal septum. It is enclosed in 

 a strong pericardium and exhibits the typical teleost form. A conspicuous bulbus arteriosus is separated 

 from the large ventricle by a constriction. The visceral blood supply is remarkable for the share taken 

 by the venal portal system in draining blood from the gut. The posterior mesenteric vein, at a junction 

 where it receives gastric and intestinal tributaries, is directly confluent with the posterior part of the 

 hepatic portal. An ovarian vein joins the posterior mesenteric which then receives the caudal vein, in 

 the region of the urinary bladder, and continues forward to the kidneys as the renal portal vein. In 

 this part of its course it is closely applied to the median renal duct. Waterman has noticed that in 

 Gigantactis also, and in a similar way, the renal and hepatic portal systems compete for the venous 

 drainage of the gut. 



As Waterman found in Gigantactis, the kidneys of the new specimen of Ceratias lie far forward. 

 They are compact organs, partly embedded in the dorsal body wall above the oesophagus. Their 

 ureters join to form a single renal duct which posteriorly dilates somewhat into a tubular bladder. This 

 opens as a generous transverse slit in the shallow urinogenital cloaca. 



ABC D 



Fig. 4. Ceratias holbulli Kroyer. The esca, A,' Mancalias bifilis' , x 18. B, ' Mancalias tentaculatus' , xSi. 

 C, Antarctic specimen, x z\. D, Kroyer's type, x \\ (after Gaimard). 



Waterman attributed to juvenility the smallness of the gonads in his specimen of Gigantactis. The 

 size of the new specimen of Ceratias puts its sexual maturity beyond reasonable doubt (see p. 19), yet 

 in this fish also the gonads are remarkably small. As all the ideas on the sexual dimorphism of these 

 fishes would lead one to expect, these small gonads are indeed ovaries, and the sex of the specimen is 

 confirmed. But microscopic examination of a teased fragment of the ovary revealed unripe, transparent 

 eggs containing no yolk. Each consisted of a vitelline membrane enclosing a homogeneous cytoplasm 

 which'surrounded a large, central nucleus. The largest ova had diameters up to 16//. The presence of 

 small regressed ovaries, containing eggs in such a young stage of development, suggests a resting 

 condition in an animal characterized by a well-defined and probably short breeding season. If this 

 were general among the Ceratioidea, then it may be supposed that the solitary, sluggish and probably 

 sparsely distributed females might well achieve and pass their sexual season before any free-living males 

 happened to find them. Is it not therefore possible that a severely restricted breeding season may have 

 been a major stimulus leading to the evolution of dwarfed males which become permanently attached to 

 the females? If so, then the suggestion (Regan, 1925a; Parr, 1930, 1932) that the milting of the male 

 may be under direct hormonal control from the female acquires added significance. 



The ovaries exhibit the cystoarian condition, and are otherwise interesting in that each is strongly 

 bent upon itself into a U-shape within its integument. Each opens separately to the exterior, and the 

 paired genital openings are located within the shallow urinogenital cloaca immediately anterior to the 

 transverse slit of the urinary aperture. 



Regan's specimen had been gutted and no observations can be made upon its viscera. 



