Dr.Wulchiier's Replij to Mr. W. Phillips. 179 



terior spiracula. So far as the word proleg may signify a pro- 

 cess of the body in A?mulosa, it may be an admissible term ; 

 but the utility of the expression may be questioned, as it scarcely 

 ever adds to our knowledge of the physiology and real use of 

 the organ. In dipterous larvffi generally, whether terrestrial 

 or aquatic, it is extremely common to see the stigmata sup- 

 ported on peduncles. 



It is worth remarking that although, in these lai-vae, until 

 we arrive at the extremes of the order, there are no stigmata 

 along the sides, except the first or humeral pair ; yet on dis- 

 secting a common flesh-maggot, — in which, by the bye, the 

 tracheae form a most beautiful microscopical object, — we may 

 observe that the longitudinal trunks of these send off at equal 

 distances lateral branches just as if there were spiracula to 

 correspond with them. Nay more, in several species of dip- 

 terous larvEe we may observe the place of the deficient stig- 

 mata marked out as tubercles along the sides of the body, and 

 they become very distinct in the pupa. The prolegs, as they 

 have been termed, of the larva of Elophiliis pcndulus give a 

 curious instance of these abortive stigmata in a high state of 

 development, and what have been described in this insect as 

 the anterior pair of feet, are no other than the usual palmated 

 stigmata which occur on the humerus of the larvae of Muscidce^ 

 only they are here somewhat pedunculated. 



Reaumur and Degeer afford us mines of information ; but 

 in the present state of the science, these most valuable authors 

 must be read with the insects before us, else they will only 

 serve to lead into error. 



Having thrown out these few hints, in order to show the 

 value of generalization in natural history, I conclude, Sir, with 

 stating myself. Your very obedient servant, 



Havana, jfune 20, 1827- W. S. MacLeay. 



XXXIV. Eepli/ loMr.W. Phillips's Remarks on the Crystalline 

 Form of the Hyalosidcrile. By Dr. Walchner, Professor 

 of Chemistry, Carlsruhe. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, 

 HE Philosophical Magazine and Annals of Philosophy, 

 Number 3, contains some observations of Mr.W. Phillips, 

 on the crystalline form of the hyalosiderite, which I de- 

 scribed*, tour years ago, as a new mineral substance. As I 



♦ Diifiuisiliii Mineralof-ico-chcmica dc Hi/alosiderilc. Frilnirgi 1822; and 

 Schweifiger's Relics Journal 1823.— [See also Phil. Mag. vol. Ixiii. p. 181.— 

 Edit.] 



2 A 2 B,m 



T 



