OCR Text |
Show 18 MR. F. DAY ON RACES AND [Jan. 15, opportunity of examining along the coast of Devonshire during the past half-year. The first specimen I propose describing is a hybrid between Salmo salar and S. levenensis. O n November 25th, 1879, as detailed by m e previously (Proc. Zool. Soc. 1882, p. 751), a man arrived at Howietoun, sent over from Stirling by Mr. Napier, with some Salmon-milt obtained the previous night, and this was employed for the purpose of fertilizing some eggs from a 4-year-old Lochleven Trout. It is necessary to draw attention to the fact that the milt came from the Salmon, as the size of the spermatozoa is such as to generally render impregnation of Trout-eggs difficult in the natural state. But here the milt had been brought in a bottle packed in snow or ice, and although the cold may have caused the size of the spermatozoids to contract, it appears to m e more probable that the large eggs of these Trout possessed a comparatively large micro-pyle. Perhaps, as we find parr full of milt during the Trout-spawning season, the size of the spermatozoids preclude their impregnating the majority of the Trout-eggs which would be on the beds; for, although it has been computed that the absorbing powers of the ova extend over 30 minutes, the period during which the spermatozoids are alive in water is about 2 | minutes, and it is probable that for such a time the male Trout would hardly permit a parr to interfere with the redd. One of the progeny of the above experiment, 11 inches in length, was captured in m y presence at Plowietoun, November 14th, 1882, and I subsequently described it in full (I. c). In the island-pond two years since some more (which were tbe smallest fish) were placed, and when this pond was drained on November 28th, 1883, several were obtained. I sent three to the Economic Fish Museum at South Kensington ; one I retained for personal examination. The specimen is on the table, and, although a year older than the one I described in 1882, is of the same length, while the others were slightly smaller; and investigations into the rapidity of the growth of these fish will form a subject for inquiry next year among those which still remain. B. x. D. 12(|). P. 13. V. 10. A. 11(f). C. 19. L.l. 114. L. tr. 24/32. Caec. pyl. 69. inches. Total length of specimen 1 LO Length of head . . 2*0 Length of pectoral tin L5 Distance from snout to base of dorsal fin 4*2 Distance from snout to centre of base of caudal fin 9*0 Diameter of eye .... 0*4 Distance of eye from end of snout 0*6 Distance of eyes apart 0*7 Height of body 2*5 Preopercle forming an almost regular curve, with but very little appearance of a lower limb. Lower jaw very slightly hooked at its |