1884.] HYBRIDS AMONG THE SALMONIDjE. 33 



impregnated from Lochleven Trout-milt. The same reason which 

 appears to militate against Trout-eggs being impregnated by Salmon- 

 milt probably is the cause, i.e. the size of the spermatozoa. Thus 

 the comparatively large Locbleven Trout-eggs were fertilized from 

 the milt of the Charr ; but when the converse was tried the success 

 was much less. As the American Charr-eggs are much smaller than 

 those of the Lochleven Trout, it is reasonable to suppose the sper- 

 matozoa are also smaller, and consequently were readily absorbed ; 

 but when it was attempted to fertilize the Salmo fontinalis by the 

 milt of S. levenensis, probably the large spermatozoa did not readily 

 find entrance, thus accounting for the great proportion of unhatched 

 ova. 



Among the Salmo fario, or Brook-Trout, which in the upper poud 

 are going on for 8 years of age, a considerable amount of fungus was 

 present. It has been observed, similar to what obtains in the Loch- 

 leven variety, that the size of the eggs augments with age. 



An exceedingly interesting subject of investigation is whether we 

 possess several or only one species of River-Trout. The foregoing 

 descriptions of hybrids show that, although neither the Salmon nor 

 Lochleven Trout possesses white edges to the dorsal and anal fins 

 (such being usually restricted to the Brook-Trout), hybrids between 

 the two appear invariably to be so marked. This year's investigations 

 at Howietoun have likewise shown that such a mode of colour may 

 occur in old Lochleven Trout, especially males. 



I have several times observed that all lines of demarcation between 

 the recorded species become obliterated should the ova of these 

 fish be transmitted to foreign lauds, where, due to changes in diet, 

 temperature of the water, and other causes, Salmo ferox may be 

 raised from the egg of our common Brook-Trout. The first and 

 last arrival of the eggs of the British Brook-Trout {Salmo fario) at 

 Tasmania occurred April 24, 1864. Some of these ova were col- 

 lected by Mr. Frank Buckland from fish in the stream running 

 through Admiral Keppel's garden on the Itchen in Hampshire, 

 while Mr. Francis Francis's were obtained from a mill at Alton on 

 the Wey, and from Mr. Thurlow's mill at High Wycombe, Bucking- 

 hamshire ; and Mr. Arthur tells us that the first successful Trout- 

 hatching in Otago occurred in October 1808, from 800 eggs ob- 

 tained from the natural spawning-beds of Salmo fario, in Tasmania. 

 These, and a second lot the subsequent year, formed the whole of 

 the original stock which were first liberated in the streams in 

 November 1869. As these Trout were raised from eggs derived 

 from our southern or smallest variety, wbere the great Lake-Trout, S. 

 ferox, is not found, it is clear that S. ferox ought not to be present 

 in Otago, unless this latter fish is merely a variety of our Brook- 

 Trout. 



Mr. W. Arthur most kindly forwarded to me, in ice, from the 

 Otago Acclimatization Society, by S.S. ' Tonic,' which left Lyttel- 

 ton, New Zealand, on July 9, 1883, two specimens of Trout recently 

 taken, this being their spawning season, " They were got in a 

 small river not 20 feet wide, which runs into a freshwater lake, 



Pkoc. Zool. Soc— 1884, No. III. 3 



