1899.] ON THE BLOOD-VESSELS OF TELEOSTEAN FISHES. 939 



3. On the Relations of the Efferent Branchial Blood-vessels to 

 the " Circulus Ceplialicus " in Teleostean Fishes, By 

 W.G. RiDEWooD, D.Sc, F.L.S., Lecturer on Biology at 

 St. Mary's Hospital Medical School. 



[Received August 1, 1899.] 

 (Plates LXIII.-LXV.) 



iNTRODUCTIOIf. 



When engaged in dissecting a Herring some years ago, I \vas 

 struck by the fact that the four efferent branchial vessels all reached 

 a median vessel which was continuous behind with the dorsal aorta, 

 and that the circulus cephalicus was situated anteriorly to the first 

 pair of vessels. This condition was so totally diffei-eut from what 

 I knew to be the arrangement of the A^essels in the Cod, that 

 I examined the same parts in a third form, the Salmon, and here 

 found a condition intermediate between the two preceding. The 

 results appeared to warrant a further inquiry, and the present 

 investigation was undertaken with a view to ascertaining what 

 are tbe commonest, and what the extreme modifications of the 

 efferent branchial arteries to be met with among Teleostean 

 fishes. 



The greater part of the work was done during the summer vaca- 

 tion of 1892 at the Marine Laboratory of St. Andrews, Scotland ; 

 but owing to the difficulty of making the series of fishes thoroughly 

 representative, the investigation has been protracted over a period 

 of seven years. Late, however, as it may now appear, I take the 

 opportunity of expressing my warmest thanks to Prof. W. C. 

 Mcintosh, M.D., P.E.S., for his kindness in placing at my disposal 

 for six weeks during the summer of 1892 all the facilities that are 

 afforded by the St. Andrews Laboratory for the pi-ocuring and in- 

 jecting of the indigenous fishes. I have also to thank Prof. G. B. 

 Howes, LL.D., F.E.S., of the Eoyal College of Science, London, 

 for specimens of Perca, Trachinus, Lophius, Fistularia, Motella, 

 Ammoclytes, Silurus, Exoccetus, Eso.v, Alhula, MegalojJS, Chirocentrus, 

 and Hippocampus, and Mr. G. A. Boulenger, F.E.S., of the JN'atural 

 History Museum, for specimens of Cotnjina, Equula, Gohiiis, 

 Sphyrcena, Hemichromis, Olarias, >SaccobrancJius, Malapterurus, 

 Callichthys, Scopelus, Cobitis, Marcusenius, Balistes, Tetrodon, and 

 Orihagorisms. 



The series of forms examined includes 61 species belonging to 

 57 genera. 



