Mr. J. S. Gaskoin on a peculiar variety of Mus Musculus. 95 



of the domestic mouse, that opinions were risked as to their con- 

 stituting a different species, but on investigating the teeth of the 

 first one that died, and they proving identical, it was inferred they 

 are a lusus naturce of that species ; — if such, however, be the fact, 

 I beUeve this will prove the first instance on record in which the 

 whole litter or brood of animals or birds, have all been in exactly 

 the same state of abnormal condition, and that condition becoming 

 permanent, and continued through successive generations ; of which 

 we have here the example of two or more generations, and have 

 no knowledge whatever of when this abnormal state may have be- 

 gun ; — for, as in this exemplification, "like begets like" — " similia 

 similibus gignuntur,^^ it is fair to conclude that the two parents 

 whose progeny resembled them, had also progenitors similar to 

 themselves ; especially as they in their breeding, like genuine species 

 in the wild state, associated only with those of their own kind ; 

 thus, if the race be not extinct, successions with the same peculiari- 

 ties will be produced, and give rise to a remarkable example of the 

 origin of a new species, or variety of a species, in the genus. I have 

 made inquiries about the locality where these animals were found, 

 as to whether others had ever been observed there before they were 

 discovered, or have been met with since, and find these to have been 

 the only known instances of their occurrence. 



I am not aware that in the nests of the Rook, Corvvs fnigilegus, 

 or the Blackbird, Menda vulgaris (which I mention as being those 

 in whose productions lusus naturce are the most frequently noticed), 

 or in the nests of any other bird, more thau one individual of a 

 brood has been found, constituted in the healthy condition, and 

 having the plumage white, and the red eye of the true albino ; but 

 variations in colour, &c., may occur in any uumber, as the results of 

 physical impediments, and not natural production ; however, with 

 increase of strength and health, these generally obtain afterwards 

 their proper-coloured plumage, and are not therefore true lusus 

 naturcB. To quadrupeds I believe the rule equally applies. 



In consequence of the interesting conversation which followed the 

 reading of the foregoing paper, 1 think it proper to subjoin a few 

 other observations. 



The excellent condition and clean appearance of the animals, and 

 their well feeding and activity, left no doubt as to their healthy 

 state during the six months they were alive in my possession and 

 during the four months they were in that of Bond. A Member 

 present stated, that while they were in the Gardens he had mi- 

 croscopically examined the lamellae or branny scales which are 

 ever separating, in larger or smaller particles, from the epidermis of 

 animals, and found them the natural and healthy production. My 

 own examination of these exfoliations had led me to the same opinion. 

 I had the opportunity, and carried my inquiry still further ; I care- 

 fully examined the surface and sections of the dermoid covering with 

 low and with high microscopic powers, and with transmitted light, 

 and as opake objects, with a view to discover any hair-follicles or 



