MR. LUBBOCK ON THE THYSANURA. 441 
simply calls " rides transversales et irregulier es, " 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 a 
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 chylifere ; du reste, leur extreme 
tenuite et leur peu de consistance ne m'ont pas permis de les etudier en detail." 
I can only say that neither in Smynthurus nor in any other genus of Poduridae 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 yAijth oi 
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 
myself that there was any open communication between the two. 
Respiratory Organs.— Smynthurus breathes by means of trachea?. There are, however, 
only two large spiracles; at least I was unable to see any others; and all the larger 
trachea, even some in the posterior part of the body, were traceable up to one or other ot 
these. It is very unusual for an articulate animal to have only two spiracles ; and then- 
position is still more extraordinary, for they open on the underside of the head, imme- 
diately below the antenme. No insect is known to have spiracles either m the head or 
between this and the prothorax ; and Burmeister (Handbook of Entomology, p. 105) even 
goes so far as to state that none are ever so situated. It appears, however (see Pagen- 
stecher, Beitrage zur Anatomie der Milben), that, though in most Mites the tracheal ori- 
fices are situated at the base of the legs, yet in TromUdlum holoserkeum the spiracles 
are two in number, and, as in Smynthurus, are situated at the lower side of the head 
though not exactly in the same place, since in this species they open on the inner side oi 
the basis of the mandibles. . . 
In the Thysanura, according to Nicolet *, « Les overtures trachedennes ou stigmates, 
dont je n'ai pu decouvrir que huit, sont placees par paires sur les arceaux superieur> des 
quatre premiers segments de l'abdomen. La couleur de leur peritreme, qui est la meme 
■me celle du corps de l'insecte, lesrendtres-difficilesaapercevoir; leur forme est lu mil aire ; 
ils occupent le milieu de chaque bord lateral des segments ci-dessus mentionnes, mais * 
une distance de ce bord egale au septieme environ du diametre transversal de 1 msecte 
M. Nicolet apparently gives this description as applicable to all the Poaureiies 
(a term in which he includes the present genus) ; and it has been so understood - 
succeeding writers (see, for instance, Gervais's ' Insectes Apteres,' vol. m. p. 3So, ami ui 
Siebold's « Anatomy of the Invertebrata,' translated by Burnett, p. 438). It is, however 
incorrect as regards Smynthurus; nor does it apply to many of the true Vo 
gether 
* Nout. Mem. de la Soc. Helvetique, toI. vi. p. 38. 
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