RESPIRATOEY ORGANS. 79 



to the respiratory movements exhibited by so many 

 insects, the above explanation seems to me to throw 

 much hght on the question, which I have already 

 treated at greater length in the ' Linnean Transactions ' 

 for 1860. 



I should not have thought it necessary to allude again 

 to the subject, but that Prof. Rathke, in a posthumous 

 memoir " On the Respiratory Process in Insects " (see 

 ' Ann. and Mag. of Nat. Hist.,' 3rd ser., vol. ix, p. 105), 

 appears to have overlooked these facts, and thereby to 

 have fallen into some errors. Thus he says, " From 

 the absence of all such phenomena we might conclude 

 that in the pupge of the above-mentioned insects (Coleo- 

 ptera and Hymenoptera) the tracheary respiration is 

 entirely interrupted." And further on, " In any case 

 it is certain that the respiration of pupge can only be 

 very weak." It has, I think, been suffiisiently shown 

 that the mere absence of respiratory movements does 

 not necessarily involve such a conclusion. 



While, however, in Smynthurus Bushii the mere 

 presence of tracheae is easily detected, difficult as it 

 may be to ascertain their distribution, I have, to my 

 great astonishment, been unable to detect a trace of 

 them in the genus Fapirius. Remembering that though 

 the great Treviranus was unable to convince himself of 

 the existence of trachese in Lepisma, they have since 

 been discovered by Burmeister, and being only too well 

 aware of the difficulties attending the dissection of 

 these minute animals, I long attributed the apparent 

 absence of tracheae to my own unskilfulness ; but this 

 explanation is not, I think, tenable, and even if rudi- 

 mentary tracheae be hereafter discovered, I feel at least 

 convinced that their arrangement and distribution will 

 be found to differ altogether from those which charac- 

 terise SmyntJuirus. It must be remembered that the 

 air in the trachec© of freshly killed insects glitters like 

 threads of quicksilver; and however absurd it may 

 sound, I consider the inside of an insect, with its 

 beautiful and rich tracery of glittering tubules, to be 



