24 On the Ova of the Large Spotted Dog-fish. 



dredged together off Killinchy, Strangford lough, from a depth of be- 

 tween two and three fathoms, and having many large and remarkable 

 ova attached to them by tendrils like those on the well-known 

 "purses," as they are called, of the common dog-fish (Scyilium Ca- 

 nicula), though they evidently belonged to a different species. They 

 were new to me and interesting in several respects. To the one 

 plant of tangle were attached fourteen, to the other twelve of these 

 ova: of the fourteen, six were very old, six of "middle age," and 

 two quite fresh — of the twelve attached to the other plant, four 

 •were very old, four of middle age, and four quite fresh. Those called 

 fresh had the " white and yelk " as in a newly laid hen's egg ; from 

 those termed of middle age, the young fish had probably long since 

 escaped : none remained to bear testimony to its species. The age 

 of the different ova was denoted not only by their own appearance, 

 but by that of the mollusca, zoophytes, &c. parasitical upon them: 

 — on the oldest were Anomice an inch in diameter ; Discopora hispida, 

 Tubularia ramosa, Cellularia reptans, all full-grown ; and on them, and 

 those of middle age, were Lepralice (Johnston) of various species, 

 Nntliporce, and masses of the ova of Buccinum undatum. 



The number of ova of different ages suggested certain points of in- 

 quiry. Their deposition at three different periods of time on the same 

 plant led to the suggestion that the fish may, like certain birds, as the 

 different species of Hirundines for example, return time after time to 

 the same spot to deposit its eggs. We can indeed only infer that 

 the same individual has deposited the ova on the different occasions, 

 but the probability is in favour of such inference That the salmon 

 (Salmo Salar) returns to its native river — if not to the same " bed " 

 to spawn — we have a notable example in the north of Ireland, where, 

 from the circumstance of the fish of the adjacent rivers Bann and 

 Bush being distinguished from each other by certain peculiarities, 

 those of every age from each river in returning to the fresh water from 

 the sea are known always to seek the ascent of their native stream. 



Being unable to find any ova described like those under consider- 

 ation, I made a sketch of one and submitted it to my friend Mr. Yar- 

 rell for his opinion, together with several queries, remarking at the 

 same time, that as " the ova are evidently generically related to those 

 of <S. Canicula, the first impression is, that they are those of the 

 most nearly allied species Scyllium Catulus, especially as we find 

 those of the next nearest ally, at least among British species — Squalus 

 annulatiis. Nils. (Pristiurus melanostomus , Bonap.) — to be of a dif- 

 ferent form ; but, that if they belong to S. Catulus, which is said not 

 much to exceed S. Canicula in size, it will be singular that the ova 

 should so greatly exceed those belonging to that species as to be 

 double their size, and in consequence of their much greater strength, 

 about four times their weight. The transverse markings represented 

 in the drawing denote plaits, which give to the exterior a handsome 

 appearance ; but they are not of specific value, the surface of some 

 ova being quite smooth, of others partially or wholly plaited." It 

 was added — " Is it known how often the Set/ Ilia deposit their ova ? 



