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Show The appearance of the abnormal vessels in the other specimen, a Chilian Pintail (Dafila spinicauda), though the abnormality was essentially the same, was less striking; the right carotid ran towards the left as in the Heron, for a short distance, but seemed relatively smaller and straighter; but it similarly turned suddenly forwards, at the point of giving off the vertebral, and sent a vessel backwards to the dorsal aorta, which it joined, at the left side of it opposite the base of the heart. This specimen was not injected, but I was able, by passing a bristle down the tube, to satisfy myself that the connection between the carotid and the aorta was a functional one. I also noted that in this specimen the artery supplying the skin of the neck sprang, on the right side, from the same point as the vertebral, while on the left it was smaller and given off a little posteriorly to the vertebral. A ductus arteriosus stretched from the left side of the dorsal aorta to the left pulmonary artery. Professor G. B. Howes has kindly drawn m y attention to Professor Turner's paper on Globiocephalus svineval (Journ. Anat. & Phys. ii. p. 66, 1868), in which the existence of a closed ductus arteriosus between the aorta and pulmonary artery is recorded as occurring in that Cetacean. Messrs. Marshall and Hurst also mention it in the Rabbit. Although I have dissected examples of upwards of 90 species, the above is the only abnormal variation in the carotids which I have observed; and that in the two specimens in which it occurred it can only be regarded as an individual peculiarity I have had ample opportunities of proving, having dissected three other specimens of Nycticorax violaceus and one other of Dafila spinicauda, besides two specimens oi Nycticorax griseus and one oi Dafila bahamensis, none of which exhibited this abnormality. I find, too, that the late Prof. Garrod has examined the three first-named species, besides Nycticorax caledonicus, and has not recorded any abnormality in their carotids. It would seem therefore that this approach to the reptilian structure does not characterize any particular species or genus, but is liable to appear sporadically in individual specimens of species belonging to widely separated groups. In conclusion, I have to express m y thanks to the Society for the facilities for study which they have afforded me, and in particular to their Prosector, without whose kind tuition and assistance this communication would have been impossible. |