3896 Royal Physical Society of Edinburgh. 



Mr. R. F. Logan then read a note " On the Exuviation of Chydorus sphaericus, 

 one of the smallest of the British Entomostraca." When first observed, Mr. L. said 

 the specimen was swimming about along with another of the same species, but soon 

 attached itself by the feet to portions of the decayed grass and Conferva? under the mi- 

 croscope, and, when disturbed from one station, speedily assumed another. At last it 

 fixed itself on a piece of Conferva, with its back uppermost, and commenced contort- 

 ing and bending itself within the shell, which speedily ruptured across the centre of 

 the back, (as shown in an interesting drawing exhibited by Mr. Logan) ; and in a few 

 seconds the animal withdrew itself, leaving the exuvia perfectly entire, with the excep- 

 tion of the fissure across the carapace. The whole proceeding did not last more than 

 two or three minutes ; and in the course of as many more it was swimming about again 

 as lively as ever, a little paler and more transparent at first, but rapidly assuming its 

 ordinary colour. 



Dr. John Alex. Smith exhibited a specimen of a black-coloured duck, of which, he 

 said, he was rather puzzled to distinguish the species. It belonged to the genus Anas 

 of Gray's ' Genera of Birds,' and bore a considerable resemblance to the mallard. Its 

 colour, however, is entirely a dusky brownish black on the upper parts of the head and 

 body, slightly glossed with green and'purple reflections ; the under parts are more of a 

 brown colour, the chin and lower parts of the head mottled with grayish brown ; a very 

 small whitish spot on the lower part of the neck in front ; under parts of the body dark 

 brown, edged with lighter brown ; sides and abdomen dusky brown ; under tail-coverts 

 edged with lighter brown ; the primaries and their coverts are dusky brown, seconda- 

 ries darker, the dull speculum dark green, glossed with purple, and faintly edged with 

 light brown ; under the wings the colours are light grayish white, the lesser coverts 

 dusky brown, edged with grayish white, the axillaries being of this light colour on the 

 one side, and dusky on the other. The bill was greenish dusky, the nail black ; the 

 tarsi and feet were reddish orange, the webs dusky, the hind toe small, slightly edged 

 with a membrane. The bird, when stuffed, measured 23 inches from the bill to the 

 extremity of the tail ; bill, 2^ inches along the ridge ; wing from flexure, 10£ inches ; 

 length of tarsus, 2 inches ; middle toe, 2\ inches; hind toe, \ an inch. Dr. Smith 

 said he had examined the body of the bird, and found that the trachea was without 

 dilatation, the bird being a female ; the stomach was a powerful gizzard, 2\ inches 

 across, and contained some small pieces of white quartz, and apparently the remains 

 of aquatic larvae. The intestine was 59 inches, and the two cceca were 5| and 6i 

 inches long. Dr. Smith remarked that it did not agree with the description of any of 

 our British birds, and appeared to him somewhat to resemble that of the dusky duck 

 of North America (Anas obscura), with which it agreed in general dimensions, but 

 which he believed was quite unknown in Europe; or it might more probably be one of 

 those strange hybrids which occur among ducks, as with the mallard and Muscovy 

 duck. The bird was in perfect and unbroken plumage, and had not the slightest ap- 

 pearance of having escaped from confinement. He was indebted to Mr. John Dick- 

 son, jun., gun-maker, Prince's Street, for being able to exhibit the bird, and that gen- 

 tleman had also favoured him with a few particulars of its capture. It was shot on 

 the river Ouse, not far from York, on the 1 1th of February, and when first observed, was 

 flying high in the air with other ducks. When closely watched, it was found that they 

 were three in number — which, by the way, is rather against the idea of their being hy- 

 brids. One was supposed to be a male, its general plumage being described as of a 



