( 240 ) 

 NOTES AND MEMOEANDA. 



The Darwinian Question. A Prize Essay.— It seems that by the 

 provisions of the late Dr. William J, Walker's foundation two prizes 

 are annually offered by the Boston Society of Natural History for the 

 best memoirs, written in the English language, on subjects proposed 

 by a committee aj)pointed by the Council. For the best memoir pre- 

 sented, a prize of sixty dollars may be awarded; if, however, the 

 memoii' be one of marked merit, the amount may be increased, at the 

 discretion of the committee, to one hundred dollars. For the memoir 

 next in value, a sum not exceeding fifty dollars may be given ; but 

 neither of these prizes are to be awarded unless the papers under con- 

 sideration are deemed of adequate merits. 



Memoirs offered in competition for these prizes must be forwarded 

 on or before April 1st, 1872, prepaid and addressed 



" Boston Society of Natural History, 



for the Committee on the Walker Prizes, 



Boston, Mass." 



Each memoir must be accompanied by a sealed envelope enclosing 

 the author's name, and superscribed by a motto corresponding to one 

 borne by the manuscript. 



Subject of the Annual Prize for 1872. — " The Darwinian Question; 

 its bearings on the development of animal life." 



The Application of Mr. Darwin's Theory to Flowers and the 

 insects which visit them, by Dr. Erm Miiller, with notes by Prof. F. 

 Delpino, is now published in English. It has been translated from 

 the Italian by an American naturalist, and may be had for 25 cents by 

 addressing to the Natm-alists' Agency, Salem, Massachusetts. 



Dr. Dudgeon's Microscope. — A writer in the 'American Natu- 

 ralist ' for September, comments on this instrument: he says that while 

 the common "tank microscope" can be worked best somewhat hori- 

 zontally, through the side of the tank, this arrangement, besides being 

 aj)plicable to much higher powers, is adapted to give a more or less 

 vertical view, being entirely free from any tremor on accoimt of the 

 motion of the toj) of the water, and is therefore especially useful for 

 dissecting purposes. Its object, though not its method, is identical 

 with that of ToUes' immersion objective for low powers, published 

 more than two years ago ; though the latter naturally possesses — being 

 constructed especially for this use, and dispensing with two unneces- 

 sary surfaces of glass — some optical superiority, as well as a much longer 

 working focus. The submersion tube, being aj)plicable to ordinary 

 lenses, only slightly lowering their magnifying power and considerably 

 shortening their working focus, will doubtless be extensively useful ; 

 though the statement that it may be always retained in position as a 

 protecting cover to the Ions without impairing the definition or illu- 

 mination in ordinary work, must be considered as too enthusiastic It 

 is especially applicable to lenses of from one inch to one-quarter inch 



