200 BULLETIN OF THE BUREAU OF FISHERIES. 



SUMMARY. 



The Salmonidae have a ventral mesentery extending from near the ventral fin 

 region to the posterior end of the abdominal cavity. The Coregonidae and Osmeridae 

 appear to have no ^'entral mesentery. 



The ovaries of the three families mentioned (Salmonidae, Coregonids, and Osmeridae), 

 are structurally similar, consisting of a membranous covering continuous with the 

 mesovarium and almost completely enveloping the ovigerous stroma. 



A practically complete envelopment is formed by the position of the ovary and the 

 mesovarium. The ovary is usually so inclined that the otherwise uncovered portion 

 is protected by the mesovarium.' The prolongation backward of the mesovariums and 

 ovarian investments form the oviducts, which in the Salmonidae and Coregonidae are trough- 

 like, open above, the inner wall consisting of the mesovarium and the free outer wall 

 (fig. 7 /) supported by the abdominal wall. Near the outlet, the two troughs unite 

 intoone above the intestine at the point of termination of the dorsal mesentery. At a short 

 distance from the genital orifice each outer wall of the common channel is deflected and 

 is attached to the respective wall of the abdomen. 



The smelt differs from the other forms mentioned only in the position of the ovaries 

 and in the extent of the lateraly deflected portion of the oviducts. 



RELATIONSHIP OF SALMONOID FISHES, GANOIDS, AND ELASMOBRANCHS AS 

 INDICATED BY THE OVIDUCTS. 



A discussion of the origin and development of the oviduct in its relation to the 

 nephridial system, concerning which morphologists still entertain different views, is 

 not pertinent to this paper, but a brief consideration of the oviducts of other fishes 

 may have some bearing upon the question of how widely the salmonoids differ from 

 the other forms respecting these structures. Huxley wrote that, whatever their mor- 

 phological nature, the arrangement of the membranes in the smelt in a physiological 

 sense was, obviously, comparable to that of Fallopian tubes, and that everyone 

 who was familiar with the anatomy of the female reproductive organs of the ganoids 

 would at once perceive that these passages are the homologues of the oviducts of 

 Acipenser, Polyodon, Polypterus, and Amia. 



Huxley observed no difference in structure or essential anatomical relation of the 

 oviducts of the smelt and the ganoids mentioned. In the structure and relations of its 

 oviduct, he regarded Osmerus as forming the third term of a series of modifications, 



1 In two humpback salmon there appeared tobemoreorlessfreeeggsurfaceon the upper outer side of the left ovary, as though 

 the ovary had been unduly stretched by the growing ova, and the surface usually inclined inward had been crowded so as to seem 

 somewhat outward. The most marked instance was as follows: 



The left ovary is about 250 mm. long, and about 45 mm. in vertical height near the posterior end of the lobe of the liver, 

 extending to the outlet. The mesovarium is attached to the upper edge — the ovarian membrane comes up on the outside a 

 little over one-third the width of ovary, making the exposed egg area comparatively wide. 



About at the point of anterior attachment of the ventral mesentery, the ovary passes up to the top of the intestine. Then its 

 vertical height is 25 mm. The end of the ovary within its almost completely infolding membrane lies in the trough with the free 

 egg surface nearly dorsal. 



The dorsal mesentery ends about 60 mm. from the posterior end of ovary. A little anterior to this, the mesovarium leaves 

 the dorsal attachment and extends free on the inner side of the top of the ovary, lying in the trough (due to the prolongation ol 

 the ovary backwaid). 



The right ovary is nearly 190 mm. long and 42 mm. wide, at about the anterior end of spleen. At this place is the only free 

 egg space to be seen without tipping the ovary. This space is semioval in shape. These membranes are 14 mm. in narrowest 

 place. The outer edge of membrane at posterior end runs diagonally across to mesentery' and extends downward to form the 

 side of the dorso-intestinal trough. 



