252 



THE CABINET OF NATURAL HISTORY 



that the animal economy of these two molluscse is singularly- 

 adapted to their mutual benefit; the velella supplj'ing nour- 

 ishment and a floating apparatus to the ianthina, and the 

 ianthina, by its attachment below so balancing and ballasting 

 the velelloe, as to preserve it in an upright position, which 

 is necessary to its motions through the water. However 

 this may be, there appeared, upon closely examining a 

 great number, but little injury sustained by the velellse from 

 its parasite. Some of the adhering shells were quite young, 

 and others full grown specimens. As far as my knowledge 

 in natural history extends, the ianthina was never before 

 ascertained to be parastitic to the velella, or made use of 

 its buoyancy on the surface of the waves to supply the place 

 of its own beautiful apparatus of air cells. This fact con- 

 firms the acuteness of Cuvier, that accurate observer of na- 

 ture, who justly concluded that the ordinary floating appa- 

 ratus of the iantliina was sometimes naturally absent; as, in 

 some specimens of the animal which he examined, not a 

 vestige of that organ could be perceived, and no scar or cica- 

 trix on the foot, by which it is secreted, could, on the most 

 minute examination, be discovered. 



Both the ianthina and velella seem to throw out a violet 

 coloured liquid, when first captured. The purple fluid dis- 

 charged by these animals will stain a white handkerchief a 

 fine rich colour. As the ianthina is often found in the 

 Mediterranean sea, it has been suggested, with some plau- 

 sibility, that this purple fluid may be the basis of the Tyrian 

 dye, or ancient royal purple, accidentally discovered by the 

 dog of Hercules. I regret very much that I could not try 

 the effect of acids and alkalies on this colour. According 

 to Pliny, alkalies gave it a green tint; if so, it is analogous 

 to a vegetable blue or purple. We are informed by Stavo- 

 rinus, that when the liquid obtained from the ianthina is 

 evaporated to dryness, a powder is obtained, which, on 

 being mixed with gum-water, forms a beautiful purple paint. 

 Since writing the above, I find, in a late foreign journal, 

 that Mr. Lesson has satisfactorily proved that the Tyrian 

 purple, noticed by Pliny, was undoubtedly derived from 

 the ianthina. He states, from some imperfect trials, that 

 the colour of the ianthina will form a valuable re-agent, for 

 it passes very readily to red, under the action of acids, and 

 returns to blue under that of alkalies. With the oxalate of 

 ammonia it gives a precipitate of a dark blue colour, and 

 with the nitrate of silver a very pleasant greyish blue, both 

 of which are good colours for drawing. 



I am doubtful as to the specific name both of the ianthina 

 and velella above noticed. The velella approaches very 

 near to the V. muiica, but the tentaculae on the under sur- 

 face cover it completely, except a narrow space at the mar- 

 gin, and a small portion immediately round the mouth; 

 they are also longer near the margin, and gradually dimin- 



ish in length as they recede inwards. If the animal proves 

 to be new, I shall call it Velella allanlica. 



The ianthina is very closely allied to the /. globosa 

 figured in Swainson's Zoological Illustrations, though the 

 shell is by no means so large and beautifully coloured as 

 those there represented. 



SUMMER DUCK, OR WOOD DUCK. 

 [Plate XXII.] 



Le. Canard (VEte, Briss. vi. p. 351. ll.;:»/. ^2. fig. 2. — 

 Le beau Canard huppe, Buff, ix, p. 245. — PI. Enl. 

 980. 981. — Summer DuchjCxTEsvY,!, pi. 97. — Edw. 

 pi. \0\.—Jlrct. Zool. No. 943. — Lath. S^/n. in. p. 

 546. — Anas sponsa, Gmel. Syst. i, p. 539, No. 43. — 

 Ind. Orn. p. 876, No. 97. — Philadelphia Museum. 



"This most beautiful of all our Ducks, has probably no 

 superior among its whole tribe for richness and variety of 

 colours. It is called the Wood Duck, from the circum- 

 stance of its breeding in hollow trees ; and the Summer 

 Duck, from remaining with us chiefly during the summer. 

 It is familiarly known in every quarter of the United States, 

 from Florida to Lake Ontario, in the neighbourhood of 

 which latter place I have myself met with it in October. 

 It rarely visits the seashore, or salt marshes; its favourite 

 haunts being the solitary deep and muddy creeks, ponds, 

 and mill dams of the interior, making its nest frequently in 

 old hollow trees that overhang the water. 



The Summer Duck is equally well known in Mexico and 

 many of the West India islands. During the whole of our 

 winters they are occasionally seen in the States south of the 

 Potomac. On the tenth of January I met with two on a 

 creek near Petersburg in Virginia. In the more northern 

 districts, however, they are migratory. In Pennsylvania 

 the female usually begins to lay late in April or early in 

 May. Instances have been known where the nest was con- 

 structed of a few sticks laid in a fork of the branches; usu- 

 ally, however, the inside of a hollow tree is selected for 

 this purpose. On the eighteenth of May I visited a tree 

 containing the nest of a Summer Duck, on the banks of 

 Tuckahoe river. New Jersey. It was an old grotesque 

 wiiite oak, whose top had been torn off by a storm. It 

 stood on the declivity of the bank, about twenty yards from 

 the water. In this hollow and broken top, and about six 

 feet down, on the soft decayed wood, lay thirteen eggs, 

 snugly covered with down, doubtless taken from the breast 

 of the bird. These eggs were of an exact oval shape, less 



