a Family of Thysanura. 371 
of greater consistency than any of the others; the colour is a 
dark yellowish brown, even in young individuals, where the rest 
of the body, or at any rate the greater part of it, is milk-white. 
The general shape is prismatic, and the section tolerably rect- 
angular, the sides being formed by the perpendicular pleural 
shields, so that the skin connecting them with the ventral and 
dorsal shields does not appear in view. Connected with the 
dorsal shield of this segment, in the middle of its posterior 
margin, we observe the small, short and broad anal plate, under 
which the anus is situated. With regard to the term anal plate 
(lamina analis), I refer to my paper on Forficula*: it is the 
same as L. Duthiers’s endecato tergite; but I see no reason for 
interpreting it as the remains of an eleventh ring; and it has, 
of course, nothing to do with the entirely superfluous term 
lamina supra-analis, which is sometimes applied to the tenth 
dorsal shield in Ulonata. 
_ Comparing the structure of the posterior part of the abdomen 
in Campodea and Forficula, the matter stands thus :—In Cam- 
podea all ten abdomen-rings are perfectly and equally developed; 
in Japye the requirements of the forceps cause a dispropor- 
tionate development of the tenth ring, whilst the ninth is some- 
what reduced and its ventral shield divided into two triangular 
plates. In both these genera the anus opens at the extremity 
of the abdomen. In Forficula there are also ten distinct abdo- 
men-rings, of which the first (segmentum mediale), as in most 
insects, is closely connected with the thorax ; here, too, the last 
or tenth ring is disproportionately large; but whilst in Japyx 
the dorsal and ventral shields are about equally developed, the 
dorsal shield preponderates very much in Forficula, the anal 
plate is proportionally larger, the ventral shield divided into 
two triangular plates, and the anus is drawn back from the ex- 
_tremity of the body, and opens at the root of the tenth ring, 
instead of at its apex, between the two halves of the tenth ventral 
shield. Besides, the eighth and ninth rings are almost rudi- 
mentary in the female Forficula. 
The short but powerful hooked branches of the forceps of 
Japyz possess regular condyles and corresponding sockets both 
in the ventral and in the dorsal shield, just as in Forficula; but 
Iam unable to say with certainty whether the forceps present 
sexual differences, as is the case in Forficula, as I have not been 
able to sacrifice a sufficient number of individuals for dissection, 
but I do not consider it probable. The spiracles are situated in 
the side folds of the first ten rings. 
The ganglia of the nervous system are large and round; each 
* Nat. Tidsskrift, 3 ser. vol. ii. p. 446. [Comp. Ann. & Mag. Nat. Hist. 
ser. 3. vol. xv. p. 484.—TRANSLATOR’S note.] ‘ on 
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