156 Miscellaneous. 



meter, and are filled with a yellowish fluid, and a fine purplish gra- 

 nular matter, which in mass gives them a dark purple colour, and 

 which, in the aggregate of the cells, gives the glands a very deep pur- 

 ple or almost black colour. When the cells are compressed, or the 

 contents pressed out, the granules exhibit lively molecular movement. 



In the centre of the mass of granular matter of the cell, and only 

 seen upon compressing the latter, is a round, translucent nucleus, 

 measuring the 1-5 000th inch in diameter, and containing a minute 

 refractive nucleolus. 



The secreting cells vary in colour in different insects, and in the ag- 

 gregate give the colour to the glandular bgdies. The reservoir also is 

 lined with cells. In Ujns Pennsylvanica they are brownish, or nearly 

 colourless, measure the l-750thinch in diameter, contain some finely 

 granular brownish matter, and a large round or oval translucent, 

 faintly granular nucleus, measuring 1-1 250th inch, with a large, 

 round or oval nucleolus 1 -2727th inch in diameter. 



The secretion of the glands of Julus marginatus, contained within 

 the interior of the body, is deep yellow in colour, and contains a few 

 of the purplish granules of the cells. It resembles oil in consistence, 

 but is soluble in water and alcohol. It is neither acid nor alkaline ; 

 evaporates at a temperature of 250° F., without residue ; is acrid to 

 the tongue, Schneiderian membrane, and conjunctiva ; smells like hy- 

 driodic acid, and stains the cuticle brown. The last two properties 

 led me to suspect the existence of iodine, but the usual reagents pre- 

 sented none. It probably belongs to a class of peculiar organic com- 

 pounds, found in the odoriferous principles of animals, not yet in- 

 vestigated. 



Exteriorly the reservoirs of the odoriferous glands of insects are 

 furnished with transverse muscular bands of a brownish colour, about 

 1- 1578th inch in breadth, and separated by wide intervals. 



In Julus the body of the glands possesses no distinct muscular 

 bands, but the neck is provided with them. — Proceedings of the Aca- 

 demy of Natural Sciences of Philadelphia, vol. iv. p. 234. 



JOURNEY TO EXPLORE THE NATURAL HISTORY OF SOUTH AMERICA. 



To the Editors of the Annals of Natural History. 

 Gentlemen, 24 Bloomsbury Street, Jan. 19, 1850. 



In the January Number of your valuable Magazine for 1849, you 

 were good enough to insert extracts from a letter I had received from 

 Messrs. Wallace and Bates, two gentlemen who are investigating the 

 Natural History of the Amazon River and its tributaries in South 

 America, and who consign their collections to me for sale. I now 

 send you extracts from a letter just received from Mr. Wallace, dated 

 Sautarem, Sept. 12, 1849, which, if you think suflficiently interesting, 

 you may perhaps feel inclined to insert : — 



'* I have got thus far up the river, and take the opportunity of 

 sending you a few lines. To come here, though such a short distance, 

 took me a month. I am now waiting here to get to Montalegre, but 

 the difficiilties of getting men even for a few days are very great. Here 



