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The Embryology of Heterodontus japonicus 703 



30 mm. The smaller ovocytes remaining in the ovary are all 12 mm. or less in diameter. 

 It is not known whether H. francisci, like H. japonicus, matures and deposits its eggs in 

 pairs; but it is possible that this may be the case, for the ovary under consideration had 

 been injured in making a large incision in the body wall to admit the preserving fluid. 

 From this opening, part of the ovary protruded, and one large mutilated follicle contained 

 only a few fragments of an egg. The mesentery supporting the ovary extends posteriorly 

 almost to the rectal gland. Throughout much of its extent it is thickened by what 

 appears to be a posterior sterile portion of the ovary. This is probably the "epigonal 

 organ" of certain sharks, which extends from the ovary along the dorsal body wall 

 posteriorly to where it joins the mesentery of the rectal gland (Daniel, 1922, p. 316). On 

 the left side of the body the ovary is rudimentary — so slender and smooth that it could 

 scarcely be recognised as an ovary except by position and relations. The epigonal organ 

 is much larger — quite as large as the one on the right side. The right and left epigonal 

 organs differ in shape: the one on the right is broader and thicker anteriorly, tapering 

 posteriorly; the reverse is true of the one on the left. Ovary and epigonal organ of the 

 left side (like those on the right) are continuous structures, supported by a single con' 

 tinuous mesentery. 



Among Dean's records I find a drawing of a dissection showing the reproductive 

 organs of an adult female Heterodontus japonicus. This drawing (my Text'figure 35) is 

 not labelled, nor is it described in Dean's notes, and in the absence of the dissection some 

 features are obscure. In the mid'line near the top of the figure, one readily notes the 

 common abdominal opening of the oviducts. On the extreme right side of the figure 

 (left side of the fish) the oviduct with its three divisions — oviduct proper, shell gland and 

 uterine portion— are easily identified. Halfway between the oviduct and the middine of 

 the body there is an elongated object of which the anterior portion is a rudimentary 

 ovary, the posterior larger portion the epigonal organ. This rudimentary ovary is not so 

 slender as the corresponding ovary of H. francisci described in the preceding paragraph. 

 The rectal gland is visible in the middine near the lower end of the abdominal cavity. On 

 the left side of the figure (right side of the fish) the oviduct, excepting the posterior end 

 of its uterine portion, is obscured by other organs. Apparently the intestine, which 

 together with the stomach occupies a large part of the left side of the figure, has been 

 transected at its posterior end to aid in turning it aside. The relations of the mesenteries 

 on this side of the fish are obscure. It is probable that the epigonal organ of the right side 

 of the fish is concealed by the stomach and intestines. It is unfortunate that these organs 

 were not removed. The right ovary is conspicuous in the upper left part of the figure, and 

 this organ deserves special consideration. 



The right ovary shown in Text-figure 35 contains a number of large eggs, of which 

 two are larger than the others. In one fish, Dean observed two ovarian eggs which were 

 almost ripe, showing large "stigmata" (orange spots or germinal discs?). The other eggs 

 of the same ovary were smaller. Nothing is written concerning the condition of the 

 eggs, if any, in the other ovary. It is not known whether the fish whose ovarian eggs are 



