MR. LUBBOCK ON THE THYSANURA. 441 



simply calls " rides transyersales et irreguliferes," though in the specimens examined by 

 me they were more distinct and regular than those of the other series. 



I found no posterior division of the stomach sufficiently well marked to justify M. 

 Nicolet's name of "intestine grele;" and the rectum, which M. Nicolet describes as 

 being " parfaitement lisse," was in my specimens distinctly muscular. He calls it 

 "csecum," which, however, is no doubt a mere slip of the pen. The most essential 

 difference between us, however, is as to the Malpighian vessels, of which M. Nicolet 

 thinks that there are six, " tubuleux et filiformes ou du meme diametre dans toute leur 

 longueur ; ils sont inseres immediatement au-dessus du retrecissement pylorique ; leur 

 longueur egale a peine la moitie de celle du ventricule chylif ere ; du reste, leur extreme 

 t^nuite et leur pen de consistance ne m'ont pas permis de les etudier en detail." 



I can only say that neither in Smyntlmrus nor in any other genus of Podm'idse which 

 I have examined, have I been able to detect any trace of these organs. 



The fatty tissue consists of lobular, opaque, white masses, which owe their appearance to 

 the presence of innumerable granules. These vary from a very minute size up to g o\) o ^h of 

 an inch, and are probably excretory products. A large band of it lies on each side of the 

 intestinal canal, with which it has numerous connexions, though I could not convince 

 myseK that there was any open communication between the two. 



Respiratory Organs. — Smyntlmrus breathes by means of tracheae. There are, however, 

 only two large spiracles ; at least I was unable to see any others ; and all the larger 

 tracheae, even some in the posterior part of the body, were traceable up to one or other of 

 these. It is very unusual for an articulate animal to have only two spiracles; and then- 

 position is stUl more extraordinary, for they open on the underside of the head, imme- 

 diately below the antennte. No insect is known to have spiracles either in the head or 

 between this and the prothorax ; and Btu'meister (Handbook of Entomology, p. 165) even 

 goes so far as to state that none are ever so situated. It appears, however (see Pagen- 

 stecher, Beitrage zur Anatomic der Milben), that, though in most Mites the tracheal ori- 

 fices are situated at the base of the legs, yet in Trombidkim holosericetim the spiracles 

 are two in number, and, as in Smynthti?'ti,s, are situated at the lower side of the head, 

 though not exactly iu the same place, since in this species they open on the inner side of 

 the basis of the mandibles. 



In the Thysanura, according to Nicolet *, " Les ouvertures trachedennes ou stigmates, 

 dont je n'ai pu decouvrir que huit, sont placees par paires sur les arceaux superieurs des 

 quatre premiers segments de I'abdomen. La couleur de leur p&'itreme, qui est la meme 

 que celle du corps de I'insecte, lesrendtres-difficUesaapercevoir; leur forme est lunulaire ; 

 ils occupent le milieu de chaque bord lateral des segments ci-dessus mentionnes, mais a 

 une distance de ce bord egale au septieme environ du diametre transversal de I'insecte." 



M. Nicolet apparently gives this description as applicable to aU the Podurelles 

 (a term ia which he includes the present genus) ; and it has been so tmderstood by 

 succeeding writers (see, for instance, Gervais's ' Insectes Apteres,' vol. iii. p. 385, and Von 

 Siebold's ' Anatomy of the Invertebrata,' translated by Burnett, p. 438). It is, hoAvever, 

 altogether incorrect as regards SmyntJiurus ; nor does it apply to many of the true Po- 



* Nouv. Mem. de la Soc. Helvetique, vol. vi. p. 38. 



3o2 



