390 Scitntijic Intelligence — Zoology. 



vided with it liave need of less light than others. The light, in 

 fact, traverses the nervous expansion in animals with a black cho- 

 roid only once, while it traverses it twice in animals with a tapetum. 



The memoir, the little of which has been given above, is a con- 

 tinuation of the first. The author first studies the colour of the 

 reflection from eyes with a tapetum. This colour varies considerably. 

 Seen in the evening by the light of a torch, the reflection in the 

 eyes of a dog passed successively from reddish-brown to fire-red, to 

 blue, green, light yellow, white, and even, in some dogs, to violet. 

 These variations in colour are perhaps owing, in some measure, to the 

 injection of a greater or less quantity of blood into the choroid, but 

 particularly to the changes in adjustment of the animal's eye. 



In the Mammifera, the tapetum is a membrane distinct from the 

 choroid. It contains no vessels ; it is traversed only by the blood-ves- 

 sels which unite the two layers of the choroid between which it is 

 found. In Ruminants, Pachyderms, some Marsupials, and Dolphins, 

 the tapetum is fibrous, and composed of undulating fibres, smooth and 

 transparent. But the tapetum of the dog and cat is very different; it 

 is a cellular tissue. It contains no fibres, and is composed of cells 

 more or less hexagonal, and with a transparent nucleus. In the dog 

 the diameter of these cells varies from 0*0008 to 0*0018 of an inch 

 (0*022 to 0*049 millim.) 



The author has not found this tapetum in the eye of birds or rep- 

 tiles. In fishes, the tapetum is composed of cells, in which are ar- 

 ranged crystals, which give it a silvery reflection. These cells are 

 elongated and flattened ; their largest diameter is four times greater 

 than that of the tapetum of carnivora. 



Lastly, M. Brucke gives the comparative anatomy of the tapetum 

 in the diff'erent orders of Mammifera, and fishes in which he found it. 



A. L. P. 



26. Memoir Illustrative of the History of the Lamentins of 

 America. By Professor Herman Stannius, Rostock, 1845, 4to. 

 — In this memoir M. Stannius gives a detailed description of 

 the diflferent parts of the American Lamentin ; he has, in parti- 

 cular, collected many interesting facts respecting the osteology, den- 

 tition, the form of the nostrils, of the mouth and lips, the larynx 

 and trachsean artery, the vascular system of the periphery and the 

 muscles. Two well-executed plates explain the most important 

 facts. 



The form of the cranium leads the author to think that the rivers 

 of America produce at least two species of Lamentin. The first 

 (Manatus Americanus, Cuv., Australis^ Blainv. Exunguis, Mus. 

 Vienne) is the smallest, and inhabits the rivers of Brazil, and prin- 

 cipally the Amazon. The second (B'lanatus latirostris, Harlan, 

 Americanos, Home, &c,), is found in Florida, the Antilles and 

 Guyana. 



M. Stannius thinks that the Lamentins, the Dugongs, and the 



