402 Proceedings of the British Association. 



3d, The description given by Cuvier (Le9ons, vol. iv. p. 258), 

 of the division of the caudal portion of the aorta, requires to be cor- 

 rected, inasmuch as the vessel is not wholly and suddenly resolved 

 into small branches, which unite to form it anew, but is only di- 

 minished in size, and concealed in the midst of a plexus of small 

 vessels, from which it again comes out. 



4th, Several arteries shew a tendency to divide into long parallel 

 branches, of which the arteries of the ploric viscera offer a striking 

 example. 



5th, The brachial artery, as in taidigrade animals, divides into 

 many long branches, which unite again into a iew larger vessels, 

 after forming a plexus which is not convoluted. 



Lastly, The internal carotid, which at its origin is as large as in 

 man, diminishes in a tapering manner, and without giving off 

 branches till it enters the skull, when it is scarcely thicker than a 

 pin. 



Some remarks were made by Dr Roget, Mr Clift, Mr Dick, Dr 

 Cooke of Durham, and Mr Mackenzie. 



A communication from Mr Murray of Hull, on the change of 

 colour in the Chameleon, was next submitted to the Section. 



After pointing out that there are other animals besides the cha- 

 meleon, such as the agama or Mexican chameleon, and the polychlo- 

 rtiSj which display a change of colour, or variable intensity in the 

 tint on their skin, and noticing some of the more striking circum- 

 stances in the natural history of the chameleon, particularly the 

 manner in which it casts its skin every six months, the author pro- 

 ceeded to describe the circumstances in which he conceives the 

 changes of colour in the skin of this animal to depend. These he 

 conceives to be the electro-chemical action of the sunbeam on the 

 blood, through the cutaneous surface, as modified by its more or less 

 accelerated impulse, conjoined with the greater or less dilatation of 

 the investing membrane. According to the author, the skin, when 

 narrowly inspected, seems to be covered with small granulations of 

 variable size, and ever varying convexity, and which are capable of 

 receiving, through the agency of a plexus of contractile and expan- 

 sive fibrillae, a variable quantity of blood. As confirming the opi- 

 nion that the change of colour is intimately connected with the cir- 

 culation of the blood, Mr Murray refers to experiments which ap- 

 pear to hinv fully to prove, that the various shades of colour displayed 

 in patches on the skin of the chameleon, exhibit corresponding 

 I'hangcs of temperature, the tliermometer indicating, according to 



