446 R. I. POOOCK. 



by a single stigma which results from the upward migration 

 and coalescence of the normal pair of stigmata upon tlie 

 first, third, fifth, eighth, tenth, twelfth, and fourteenth 

 somites — a change in the method of respiration which is 

 accompanied by the complete disappearance of the tergum 

 of the seventh somite, either by excalation or by fusion with 

 that of the eighth, and by the evanescence of all the minor 

 tei-ga except that of the fifteenth leg-bearing somite. 

 Further specialisation is attested by the presence of a 

 sense-organ on the gnathites of the second pair, by the 

 polymeniscous eyes,^ the duplication of the gonopods in the 

 male," and the extreme length and perfected annulation of 

 the antennae and of the distal segments of the legs, those 

 of the fifteenth pair being clawless and simulating a couple 

 oE feelers both in form and function. In virtue probably 

 of these extremely specialised features, mouth parts of a 

 markedly primitive type have been preserved; the long 

 and slender toxicognaths exhibiting only a partial axial 

 rotation, long penultimate segments, and disunited and in- 

 dependently moveable coxaj, the palpognaths being also 

 incompletely rotated, long and pediform, with the same 

 number of segments as the primitive Chilopod limb, and 

 projecting freely at the sides of the head ; the prasantennal 

 area of the cephalite projects forwards and downwards in 

 front of the bases of the antennte, which remain widely 

 separated as tliey are in the early embryonic stages in this 



' I liere provisionally adopt the view already suggested by others, that the 

 faceted eye of Scutigera resulted from the packing together and mutual 

 pressure of a number of mouonieuiscous eyes like those of Lithobius. But 

 in view of the many primitive features appertaining to the head of Scutigera, 

 the possibility must be borne in mind of the derivation of a set of mono- 

 meniscous eyes from one of a polymeniscous type, as has doubtless occurred 

 in the case of the lateral eyes of Scorpio. Or, again, it may be that the 

 large convex eye of Scutigera, with its many facets, corresponds as a whole, 

 either in a derivative or, originative sense, to the large single-lensed eye of 

 Cermatobius, the genus which, beyond all possibility of doubt, is most 

 nearly related to Scutigera in all other structural points. 



* Possibly the additional gonopods represent the missing appendages of the 

 anal somite. 



