74 KNOX ON THE CETA.CEA. 



the lactiferous glands in the Balanoptercd differ in structure from 

 the same organs in most mammals. 



I do not find in my notes anything to add to the description of 

 the Great Eorqual already published in the ' Transactions of the 

 Eoyal Society of Edinburgh' for 1827, to which I beg leave to 

 refer the reader. 



A single remark must be added regarding the nature of the 

 vascular plexus which, in the Cetacea, surrounds the spinal marrow, 

 and extends into the chest. On selecting the artery which seemed 

 to form the plexus, which was, if I rightly recollect, in this instance 

 an intercostal artery, and dissecting it under water, I found, to my 

 surprise, that the artery, so long as I followed it, never gave off 

 any branches, but continued of the same calibre throughout, 

 making innumerable flexuosities or turnings. Thus, on a plexi- 

 form mass of this kind being cut across, the first impression is, 

 that a great number of arterial branches or arteries have been 

 divided, whilst in fact the entire plexus seems to be formed of one 

 artery. 



As was to be expected of animals so much withdrawn from 

 human observation, there is but little to say on the natural history 

 of the Cetacea properly so called. Their food, no doubt, is va- 

 rious, and seems to have little or no relation to the character of 

 their dentition. The enormous Cachalot, with its vast teeth im- 

 planted only in one jaw, is generally understood to prey chiefly on 

 the Cuttlefish. The food of the true Whale, or Mysticetiis, is well 

 known to be the Clio and other smaller Mollusca, with which 

 certain regions of the ocean abound; the same, or similar, is 

 probably the food of the more active and restless Eorquals, found 

 in both hemispheres. The Dolphins, or Toothed Whales, generally 

 prey, no doubt, on fishes of various kinds ; yet, even as regards 

 these, it has been proved by my esteemed friend, the late 

 Mr. Henry Goodsir, that some of the largest, following in the 

 wake of the herring shoals, prey not on these, but on the various 

 microscopic food (the Entomostraca and other marine animals) 

 which I was the first to prove to be the natural food of many ex- 

 cellent gregarious freshwater fish, as the Vendace, Early Loch 

 Leven Trout, the Brown Trout of the Highland and Scottish lakes 

 generally, and of the Herring itself*. It is scarcely necessary to 

 add, that the complex apparatus connected with the exterior 



* See Memoirs in the ' Transactions of the Royal Society of Edinburgh ' 

 for 1832. 



