286 SIR JOHN LUBBOCK ON THYSANURA. 
ANATOMY. 
Intestinal Canal. 
According to Nicolet (l. c. p. 46), the digestive organs of the Thysanura consist of six 
parts—namely, l'ésophage, le jabot, le ventricule chylifére, les vaisseaux hépatiques, l'in- 
testine gréle, et le cecum.” By the “ cæcum” he evidently means the rectum. Nicolet 
gives his description of these parts as applicable to the order generally, and does not 
mention which genus or genera he particularly examined. In those which I have dis- 
sected, and particularly in Tomocerus, Orchesella, and Smynthurus, the digestive organs 
pass straight through the body without any circumvolutions from the head to the tail, 
and fall into three divisions, the cesophagus, the stomach, and the rectum. I think 
there are no Malpighian vessels. 
Von Olfers, the only naturalist who has, since my paper in the * Linnean Trans- 
actions" (which, however, he does not appear to have seen), occupied himself with the 
anatomy of the Thysanura, also describes and figures the intestinal canal, at least in 
Orchesella, as a straight tube passing directly from one end of the body to the other, and 
falling into three divisions, the cesophagus, the ventriculus, and the rectum. 
The cesophagus is rather long, narrow, and composed of an inner chitinous membrane, 
thrown more or less into folds, and a cellular envelope, outside which, again, is a loose 
and very delicate membrane. Nicolet describes a crop as existing between the cesophagus 
and the intestine stomach; but he admits that it is only *une simple dilatation de 
l'ésophage, dont le diamétre varie selon que l'insecte a plus ou moins mangé." 
Von Olfers was, I believe, the first to observe that from one side of this swelling, 
which is somewhat thickened, rises an elongated membranous tube. This he regards as 
the salivary gland ; and he considers that it really rises immediately behind the mouth, 
passing backwards along the cesophagus, to which, however, it is so firmly attached that 
* ne vi quidem separari possint" (they can hardly be separated even by force). In fact, 
if the “ salivary gland " and the stomach be pulled in opposite directions, as far as my 
experience goes, the former gives way. 
The stomach is capacious, and extends in a straight line from the posterior end of the 
esophagus to the commencement of the intestine. It is of even width throughout. 
Externally it is provided with both longitudinal and transverse muscles, which give it 
a pretty reticulated appearance (Plate XLV. fig. 13). The transverse series is the 
most numerous, the spaces between the muscles being something less than twice the 
width of the muscles themselves. In some places, as in Plate XLVI. fig. 15, they 
anastomose frequently. This appeared to me to be more the case in some specimens than 
in others. The distances between the transverse muscles are much larger. The stomach 
contains, besides the food, a large number of clear round cells containing smaller cells or 
vacuoles. It is, moreover, often occupied by a number of Gregarinas. 
According to Nicolet, the Malpighian vessels are probably six in number. He says, 
* Les vaisseaux hépatiques, dont je n'ai pu au juste reconnaitre le nombre, mais que je 
crois être de six, sont tubuleux et filiformes ou du méme diamètre dans toute leur 
