Séance du 17 Novembre 1920 8ò 



Bclween Ihc two layers and in the spaces helweeii 

 the cmieilbnii colls small ca\ili{'s can be seen which 

 may be lilled wilb plasma when llic blood overllows 

 iiilo lliem diirin;^ llic unioidini; prot'ess. 



In llie neii;lib()iirhoo(l ol (lie \'eins the chilinous 

 laminae ar(> separalt'd. The resulting s|)ace is seen in 

 the section as a rounded channt'l, clearly confined by 

 cells and causini^ a prominence on one ol' Ihe surfaces, 



ir it is a longitudinal M'in, a small light circle is seen 

 close to the wall within the lumen. This corresponds 

 to the ti"achea and around it the pcrilraeheal space can 

 be seen, much widi'r and lianslbrmed into a lube. The 

 cuneiform cells, more diawn out at this poini, and niore 

 closely |)acked, form a conlinuous wall lo this shralh. 



Hon the olher hand the section is across a tians- 

 verse or connecting vein, il can be lecogni/.ed by the 

 absence ol the trachea and the smalK-r diameter (jf Ihe 

 lumen. .\s in the preceding case, Ihe xcssel in which 

 the blood flows has a conlinuous wall formed of cells. 

 'J'he only exceptions are the breaks obserscd in a few 

 branches ; in Ihat case the \essel leiininales in a wide 

 opv n v\u\ where the wail suddenly ceases. 



These observations are not ((uile in accordance with 

 the usual descriptions of (he \ascular system of insects 

 While within (he body (he blood ciiculales in incom- 

 pletely closed lacunae there is in the wings of (he lOmpusa 

 a network with conlinuous walls composed of cells. 

 Probably similar condilions exisl in Ihe wings of Le[)i- 

 doptera. (Closed vessels, moreoxer, have been described 

 in olher j)arls of Ihe body, foi- example in Ej)liemeridae, 

 by I\)i'()vicni-HAZNO.SANr, (lOO.l-Ol)), 



The tracheal system of the wings of Orlhoptera 



