TUE STICK-IXSECT. 1 75 



The Malpigluau tubes in all Orthoptera except the Forficulida? 

 are very numerous, and ai'e geneivilly grouped in six bundles 

 opening at the summit of six tubei'cles, as in the Locustida; and 

 lilattidse. In all the Gi-yllida?, on the contrary, the Malpighian 

 tubes are arranged in a single bundle opening into the dilated 

 extremity of an unpaired excretory canal. Very charactei'istic 

 is the presence of a " ciliated border " (un revetement cilie) 

 projecting from the cells of the mid-intestine and lateral 

 appendages. 



The alimentaiy canal of B. rossli is divided into three parts, as 

 in all arthropods. 



1. Fore-gut, ectodei-mie, corresponding to the stomodaMnii, and 

 comprising the mouth, pharynx, oesophagus, and crop (PI. XXVIII. 

 fig. 1 ) ; the gizzard is absent. 



2. Mid-gut, endodermic, corresponding to the mesenteron, 

 beginning posterior to the crop and ending at the insertion of 

 the ]\Ialpighia.n tubes. The lateral cfBca, generally developed 

 from the anterior part of the mid-gut, are rudimentary in B. rossli 



(fig. 1).. 



3. Hind-gut, ectodermic, cori'esponding to the proctoda?um, 

 beginning at the insertion of tlie Ma][)ighian tubes and including 

 small intestine and rectum (lig. 1). 



In many respects the alimentary canal is peculiar, and the main 

 features which conti'ibute to its uniqueness may be tabulated 

 as follows : — 



1. The rectilineal shape of the gut, there being no con- 



volutions of the posterior region (fig. 1). 



2. The complete absence of the gizzard. 



3. The rudimentarv natui-e of the mid-gut digestive cpeca 



(figs. 1 & 3, C). 



4. The presence of numerous peculiar conical tubular 



organs on the posterior position of the mid-gut 

 (fig. 1, Ta.). 



In prepai'ing sections for histological examination of the gut 

 various stains ware employed. Grenadier's hajmatoxylin was 

 especially good in the difterentiation of chitin, while Heidenhain's 

 iron-haamatoxylin proved very efiective where epithelium was 

 concei-ned. Professor Hickson's brazilin stain and borax carmine 

 were also used to advantage. To get the best results the gut 

 re'juired lather careful treatment, and in tlie matter of a fixing 

 agent I found that Schaudimi's fluid was all that could bo 

 desired . 



It is generally accepted that the mid-gut of insects is endo- 

 dermic in its origin, but in the ease of B. rossii Heymons (1897) 

 demonstrated that it was really ectodermic, being developed from 

 two epithelial outgrowths of the stomodajum and proctodseum 

 which surround the yolk and become united. This manner of 

 formation, he maintains, may be found to hold good for all 

 Phasmida?. 



