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II. On the Distribution of the Tracheae in Insects. 

 By John Lubbock, Esq., F.B.S., F.L.S., Sfc. 



ReadJanuary 1 9th, 1860. 



Dean SWIET, m the ' Tale of a Tub,' asserts that in the world generally, and in 

 animals in particular, the outside is generally more beautiful than the inside. " Last week," 

 he says, " I saw a woman flayed ; and you will hardly believe how much it altered her 

 person for the worse." The Dean, however, does Nature an injustice. We constantly 

 find the most lovely things where we should least expect to meet with them. Many 

 insects are very beautiful externally ; but there is nothing, I think, more pleasing to the 

 eye than some parts of their internal anatomy ; and no one, I am sure, can see the 

 tracheae branching over the different organs, like trees of shining quicksilver, without 

 being both astonished and gratified. 



Although Lyonet, Straus-Dlirckheim, and many other entomologists have described 

 and figured the arrangement of the larger tracheal branches, no one has yet studied the 

 distribution of the finer branchlets. This is, no doubt, mainly owing to the fact that, 

 more or less quickly after death, fluid penetrates into them, and that they then become 

 very difficult to distinguish from the surrounding tissues. It is indeed true that there are 

 a few scattered observations on this subject ; but no one has yet compared together the 

 finer tracheae attached to the different organs of various insects, or attempted to arrive at 

 the laws regulating their distribution, — to determine, for instance, whether the type is the 

 same throughout each insect, or different in the various organs, and to compare with one 

 another insects of vai'ious families and orders. 



I ought perhaps to apologise for presenting to the Linnean Society a memoir so imper- 

 fect ; but if the marvellous number of insects be remembered, and if it be borne in mind 

 that each one contains at least from fifteen to twenty different organs to be examined 

 separately, it will be evident that no one man could hope to exhaust the subject. 



Having, therefore, to deal with a subject so vast in itself, I have confined myself strictly 

 to it. Without intending to express any opinion of my own as to their homologies and 

 functions, I allude to the various organs by the names under which they generally pass, 

 even when the generally received opinion seems to me doubtful or incorrect. 



I wish, however, to say a few words respecting the homologies of the intestine of 

 Pentatoma. It seems to be pretty generally admitted that in this group of Hemiptera, 

 the biliary vessels, either directly or through the "vesicule biliaire" of Leon Dufour, 

 pour their contents into the rectum, below the ileum. Leon Dufour*, indeed, while 



* Mem. des Savants Etransers, vol. iv. p. 153. 



