ICHTHYOLOGY. 



681 



in a vas deferens ; the underpart of which is greatly di- 

 lated, and forms, as in birds, a considerable receptacle, 

 or vesicula seminalis. Contiguous to the outer side of 

 the dilated end of the vas deferens, there is a bag of 

 considerable size, filled with a green liquor, which is 

 discharged into the same funnel with the semen, and 

 probably at the same time with it. By some, this is 

 considered as a vesicula seminalis, while by others it is 

 regarded as supplying the place of a prostate gland. 

 The funnel through which the seminal fluid is poured, 

 open* near the cloaca. 



In the males of the chondropterygii, there are cer- 

 tain organs situated near the anus, consisting of bone, 

 cartilage, and muscles. These were long regarded as 

 the external organs of reproduction. But Rondeletius 

 was of opinion that these were only accessory organs, 

 and enabled the males to retain the females more close- 

 ly during coition. The celebrated ichthyologist Bloch, 

 from dissections, arrived at the same conclusion. 



The late Mr Montagu has observed some peculiari- 

 ties in the sexes of the skate, which deserve to be no- 

 ticed. These are enumerated in the Memoirs of the 

 IVerneria* Natural History Society, vol. ii. p. 414. After 

 speaking of the appendages at the base of the tail, he 

 says, " Accompanying this truly masculine distinc- 

 tion, are series of large reclined hooked spines, never 

 to be found on the other sex, and which begin to shew 

 themselves early in all the species hitherto examined ; 

 these are placed in four distinct series, one on each 

 shoulder or fore-part of the wing, or pectoral fin, and 

 one on each angle of the wing. These spines are com- 

 plete hooks resembling those used for fishing, and lie 

 with their points reclined inwards in two or three, and 

 > four parallel lines, but the number of rows, 

 in each row, depends on age ; for in very 

 I have noticed only four or five 

 row. For what purpose this formi- 



Structurt 

 and 



armoury is given exclusively to the males, is not 

 known, bat as the hooks are extremely sharp, and lie 

 partly concealed, with their points a trifle reflected, the 

 fishermen's hands are frequently lacerated by incau- 

 tiously handling the fi.-h. These formidable spines, pe- 

 culiar to the masculine gender, have occasionally been 

 fixed on as a specific character ; and as it does not ap- 

 pear to be generally known that it is only a sexiu 1 

 distinction, it has been thought proper to notice it for 

 the advantage of others who may be pursuing the same 

 track. There is another circumstance, which perhaps, 

 in the discrimination of species, requires more attention 

 than usual ; that is, the teeth of both sexes of each 

 species. The necessity of this is particularly evinced 

 by the great difference observable in the teeth of the 

 two sexes of the thorn back, Rain cltnata. 



" In search of both sexes of this species, I was natu- 

 rally led by the usually described essential character of 

 the teeth being blunt, and I was not a little surprised 

 when, amongst several hundreds examined, not one 

 male could be found ; Imt I noticed a ray, not unfre- 

 quently taken with the thomback, that was in every 

 other respect similar, except that the wings were gene- 

 rally not so rough, and sometimes quite smooth about 

 the middle. A variety also of this fish had an oblong 

 dusky spot, surrounded with white, in the middle- oi 

 each wing. The teeth of these fishes were not above 

 half the sue of those of the female thornback, and, ex- 

 cept a few of the outer series on the lips, were sharp- 

 pointed. For a long time I was puzzled to discover to 

 what species of Kaia these belonged, till, after an exa- 



rot. xi. i ART n. 



mination of a great number, 1 began to be as much 

 surprised at not finding a female amongst such a quan- 

 tity of these, as I was at not finding a male amongst ,;, 



i ' . i_ i i mi O 01 risiies. 



those with blunt teeth. These circumstances naturally _- y _^ 

 induced me to conclude, that the sexes of clavata had 

 not l>een accurately defined, and that the leading cha- 

 racter of blunt teeth might have been drawn from the 

 female only. The fishermen had not noticed the dis- 

 tinction of the teeth in these fishes, and had considered 

 all of them to be thornbacks. After much attention 

 to the subject, and after having offered a premium for 

 a male thornback with blunt teeth, an intelligent fish- 

 erman assured me, he had examined a vast number 

 since I pointed out the distinction of the teeth, and 

 that he could not find one instance of a male with blunt 

 teeth, nor a female with sharp teeth. It may therefore 

 be fairly inferred, that the sexes of the thornback ac- 

 tually differ in this particular, and that the male h;r- 

 probably been described as a different species, but un- 

 der what title it is difficult to ascertain, unless it be 

 Raja fullonica of some authors." 



The male organs of the sharks and rays are such as we 

 have now described ; but few accurate observations have 

 been made on the male organs of those ovoviviparous 

 fishes, which belong to the branchiostegous and osseous 

 tribes, such as the sy ngnathus, blennius, and muraena. 



In the Jemales of the sharks and rays, the ovaria, 

 two in number,* arc situated at the sides of the spine, 

 and contain ova of different sizes. From each of these 

 proceeds an oviduct, the anterior extremities of which 

 are united to the diaphragm and spine. Internally. 

 these ducts are covered with glandular papilla 1 , and ; 

 through a large glandular body. After passing this 

 body, they dilate into a large sac, which is the uterus. 



When the ova pass into the oviduct, they are carried 

 to this glandular body, which is supposed to secrete the 

 glaire or albuminous part, and afterwards conveyed to 

 the uterus, where they receive the shell. At what pe- 

 riod the egg becomes impregnated, or in what manner 

 the operation is performed, are questions to which no 

 satisfactory answers can be returned. 



The eggs are of a quadrangular form, with processes 

 at the four corners. By some they are called sea-mice, 

 but by our fishermen they are known by the name of 

 skate or shark-purse*. The shell has a horny consist- 

 ence, and may often be observed, at certain seasons, 

 among the rejectamenta of the sea. 



When the young fish have been perfected in the ute- 

 rus, where they derive their nourishment exclusively 

 from the egg, and not from the mother, they are eject- 

 ed through the openings of each uterus, at the sides of 

 tin- cloaca ; and upon escaping from the shell, enjoy 

 immediately an independent existence, and begin to 

 search after new nourishment. 



3. Oviparous Jisfies which arc liermaphrodi'c. I n- Hernia- 

 stances of hermaphroditism among fishes, were for a long phroditcs. 

 period considered rare, and always as accidental. l!;i-- 

 ter detected such an arrangement in the whiting, and 

 Duhamel observed the same in;thc carp. But it was re- 

 served for that able anatomist, Sir Evernrd Home, to 

 point out a particular tribe of fishes in which the organs 

 of both sexes are always present in the game individual. 



Having been unsuccessful in obtaining any male lam- 

 prys, although he got what were considered as females 

 in abundance, Sir Everard began to suspcc-t that the 

 individuals of the species were hermaphrodites, and 

 his observation on these fieh at different periods justi- 

 fied his conjectures. 



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