darkest the surface was uneven, more or less nodulated, and felt, on pinching it up, thickened and quite firm. The margin between the discolored and natural skin was almost continuously of a light-brown color, quite definite in ex- tent, generally about 2 lines, or more, in width ; but upon the chest, and to a small extent, it was about two-thirds of an inch in width. About the top of the shoulder there was quite a development of soft hair. Upon the back of the pelvis, and left side of the trunk, there was a patch equal to an inch or more in diameter, as black as the above, and with hair upon the surface ; also a patch upon the right thigh, about half as large. Over the trunk and limbs were scattered numerous spots, of a comparatively light-brown color, generally 2 lines, or more, in diameter, and that, individually, would have been called moles. Only one of these last was found upon the head, and that was upon the upper lip, and very pale. 1870.
Mr. W. P. Bolles, med. student.
3646. A second collection of double trout, recently hatched, and from the establishment, in Barnstable, already referred to (No. 903).
On comparing them together, the following varieties were observed : In one there were two heads and two tails, but the bodies are fused. In six the two individuals were connected only by the umbilical vesicle. In one of these, one was very much atrophied, and the other largely devel- oped ; in another there was also a very considerable dis- proportion, and the same was observed, more or less, in some of the other varieties. In another specimen of the above variety, one was single, but had no eyes ; the other divided anteriorly, and one head had two eyes, but the other had none. One had two heads, with four eyes, but was otherwise single. Six were united by the posterior portion of the body, or by the tails only, and otherwise separate or double. In one specimen one is very large, and the other much atrophied. In another specimen of the last variety, one head has two eyes, and a central one between them. In three other specimens of the same vari- ety, one head has two eyes, and the other four. In one specimen the body is single posteriorly, but with two cau-
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