^^y ESTIMATE OF DARWIX. 



475 



too small to affect our retina, wbicli will be impressed by the same 

 quantity of pigment when more extended. 



It is undoubtedly the nerves which connect the brain with organs 

 where the pigment is retained. By cutting a nerve, the coloring-mat- 

 ter is paralyzed in that portion of the skin through which the nerve 

 passes, just as a muscle is isolated by the section of its nerve. If this 

 operation be performed on a turbot when in a dark state, and thrown 

 into a sandy bottom, the whole body grows paler, exce2)ting the part 

 which cannot receive cerebral influence. The nerves have, in.general, 

 a very simple and regular distribution ; if two or three of these are 

 cut in the body of the fish, a black transversal band following the 

 course of the nerve will be seen ; while, if the nerve which animates 

 the head is thus treated, the turbot, growing paler on the sand, keeps 

 a kind of black mask, which has a very curious eftect. 



These marks will remain for many weeks, and what may be called 

 paralysis of color has been remarked in consequence of illness or ac- 

 cident. Such was seen in the head of a large turbot, the body being 

 of a different color. It was watched, and died after a few days, evi- 

 dently of some injury which it had received. The subject offers a 

 field of immense inquiry ; the chemical and physical study of pig- 

 ments, the conditions which regulated their aj^pearance, their inten- 

 sity, and variations under certain influences ; the want of them in 

 albinos, and the exaggerated development in other forms of disease. 

 To Mr. Darwin, and to M. Ponchet, in France, the subject is in- 

 debted for much research, which will no doubt be continued as occa- 

 sion offers. — Chambers's Journal. 



AX ESTIMATE OF DAEWIX. 



By Professor ASA GEAY. 



TWO British naturalists, Robert Brown and Charles Darwin, have, 

 more than any others, impressed their influence upon Science in 

 this nineteenth century. Unlike as these men and their works were 

 and are, we may most readily subserve the present purpose in what 

 we are called upon to say of the latter by briefly comparing and con- 

 trasting the two. 



Robert Brown died sixteen years ago, full of years and scientific 

 honors, and he seems to have finished, several years earlier, all the 

 scientific work that he had undertaken. To the other, Charles Dar- 

 win, a f:iir number of productive years may yet remain, and are ear- 

 nestly hoped for. Both enjoyed the great advantage of being all 

 their lives long free from any exacting professional duties or cares, 

 and so were able in the main to apply themselves to research without 

 distraction and according to their bent. Both, at the beginning of 



