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Show 844 MR. GULL1VI R ON THE ANATOMY [Dec. 6, T. venustus (as characterized, I. c. si) cannot be considered from T. viridis. We have specimens of this bird now before us from Rio, Bahia, Matto Grosso, Eastern Venezuela, and Bogota, and can find no constant differences amongst them, although there is considerable diversity of tint in the colour of the lower back, and some specimens approach to what Dr. Finsch has recently proposed to call T. cyanurus (P. Z. S. 1870, p. 559). On the other hand three Panama skins (in Mus. S.-G.) present the remarkable character of the outer tail-feathers above mentioned. The first outer pair are all pure white except a narrow basal patch concealed by the tail-coverts. Of the second pair, considerably more than the apical half is white. In the third pair the white apices measure 2 in. in length. When the tail is closed the under surface appears perfectly white. W e therefore call this bird T. chionurus. We have seen other examples of this Panama species in Mr. Lawrence's and Mr. Gould's collections. 10. O n certain points in the Anatomy and Economy of the Lampreys. By G E O R G E GULLIVER, F.R.S. BLOOD-CORPUSCLES. Red Corpuscles.-For the discovery of the now well-known circular shape of the red blood-corpuscles of the Lamprey, we are indebted to that eminent physiologist Rudolph Wagner. He likened them, as biconcave disks and otherwise, to those of Man and Mammalia; and as his figures and descriptions of those of the Lamprey are the only ones with which I am acquainted, it seems to me that a further account of them is yet desirable. The majority of them are circular; only a few assume a slightly oval form, just as some circular red disks appear among the far greater number of the regular oval or suboval ones of osseous fishes. The red corpuscles of the Lamprey are but rarely or exceptionally biconcave disks, and then only from irregular or unequal depressions on the surfaces, scarcely ever from those two symmetrical concavities which are so truly characteristic of the blood-disk of Apyrensematous vertebrates. On the contrary, the red blood-corpuscles of the Lamprey are regularly either flat or slightly biconvex (fig. 1, a and b); but this form is liable to much variation from one or more dents caused by puckering or contractions inwards either of the surface or of the margin of the soft disk ; often a depression on one side and projection of the other produces a concavo-convex form; and, as a rule, the disk is proportionally and absolutely thicker than that of Apyrensematous vertebrates. The nucleus (fig. 2) is very distinct, either circular or suboval, and sufficiently thick to prevent two such central depressions on the faces of the red corpuscle as would make it a symmetrical biconcave disk. Hence the comparison of the blood-disks of the Lamprey to |
