400 Miscellaneous. 



to those of light. Above the TJnios was from one to two feet in 

 depth of clear running water, rendering everything upon the bottom 

 distinctly visible. 



Believing that the sun's radiation coming directly toward any object 

 so far beneath the surface of the water would have its heat-rays 

 mostly, if not entirely, separated from the light-rays, at or near the 

 surface, through the absorption of these and their removal down- 

 wards by the current, while nearly all the rays of light would pass 

 on to the object with only slight refraction, I sought a place where 

 rays of heat from sunlight, striking the surface further up the stream, 

 would not reach the Unio to be experimented upon. This was fur- 

 nished by a dense growth of trees, shading the stream completely 

 for a considerable distance. Then placing a Unio just at the lower 

 margin of the shade, but quite within the bright sunlight, I 

 awaited the opening of the orifices ; then, on quickly intercepting the 

 sun's rays that came freely to it, by passing a screen from above 

 downward, and again from below upward ; it responded by closing 

 its orifices as quickly as its fellows had done when my shadow 

 passed over them in the broad open space of sunlight. 



Upon the supposition that the light- and heat-rays are divided at 

 the surface of the water, as before suggested, the heat-rays must 

 all, or very nearly all, have passed down below the Unio, by the 

 action of the current, while the light-rays alone reached it, and 

 their sudden interception caused it to close its orifices. Thus in 

 this position the Unio was receiving direct rays of light from the 

 sun, but the rays of heat that might have reached it more or less 

 obliquely, by absorption and the action of the current, if in an open 

 space of sunlight, were here cut off by the long shadow of the trees. 

 Therefore no doubt is entertained that the posterior portion of these 

 mollusks is keenly sensitive to light ; but exactly what organs are 

 thus sensitive has not been ascertained. — Silliman's American Jour- 

 nal, March 1869. 



The Sea-Elephant (Morunga proboscidea) at the Falkland Islands. 

 By Dr. J. E. Gkay, F.R.S. &c. 



In the 'Annals & Mag. Nat. Hist.' for March 1868, p. 215, I 

 stated that the sea-elephant had become extinct in the Falkland 

 Islands. Mr. Sclater, in the ' Proceedings of the Zoological Society' 

 for 1868, p. 189, says that this statement was a mistake ; but in 

 his account of the proceedings of Adolphe Alexandre Lecomte, who 

 was sent by the Zoological Society to collect Sea-lions and Penguins 

 for the Collection, he now confirms my first statement, and observes, 

 " Elephant Island, so called from the former abundance of the sea- 

 elephant {Morunga proboscidea), was found to be quite deserted by 

 this animal, which is said to be now entirely extinct in the Falk- 

 lands." (See Proc. Zool. Soc. 1868, p. 527.) 



