Limbs and Mouth-parts of Crustaceans and Insects. 433 



tion may be best compared to the paragnathi of Crustacea, 

 although a homologization with the hitter structures may well 

 appear to be out of the question ") can belong to the inaxillulEe 

 is a question which must receive further elucidation from 

 future embryological investigations. 



49. In ditFereut Insects we can (with especial ease in all 

 Cicadaria in the case of all legs, with exception of the last 

 pair in Fulgorid») demonstrate the existence of a plate, which 

 moves together with the coxa and which is decidedly homo- 

 logous with the first segment in the legs of Machilis (§33) ; 

 this plate, which is termed the trochantin, consequently be- 

 comes homologous with the coxopodite in the Malacostraca. 

 It therefore does not belong to the same type of structure as 

 the mandible and the cardo of the maxilla3 (§§28, 29, and 

 25). 



60. The trochanter in the legs of Insects, as is well known, 

 often attaches itself closely to the femur, but is nevertheless 

 not to be regarded as a portion of the latter which has been 

 secondarily constricted off; on the contrary, it is to be con- 

 sidered as homologous with the ischiopodite of the Mala- 

 costracan limb. 



51. With reference to the origin of the paired claws in 

 Insects, I think that I mav make the following statement: — 

 In the Collembola we meet with a structure which agrees in 

 the closest manner with the condition discussed in § 2L in the 

 case of certain Isopods. We find that the leg ends with a 

 short but well-developed and very freely movable segment, 

 from the tip of whicli there proceeds a long and powerful 

 claw (with a somewhat large chelifornr process on each side), 

 while to the underside of tiie segnient another smaller claw is 

 articulated. If we now start from my morphological interpre- 

 tation in the case of the Mysidaj (§ 18) the short movable 

 segment becomes the penultimate segment of the foot, the 

 large claw the last segment, and the lower claw a large thorn 

 [vide a good figure in TuUberg) . In Japyx soliflujus the 

 lower claw has passed up on to tlie side of the movable seg- 

 ment, though scarcely to the same level as the large claw, 

 and it is also somewhat smaller than the latter. The tran- 

 sition to the ordinary double claws now becomes very simple. 

 1 recommend the foot of a large Acridium for examination ; 

 the claws have here attained an equal size and proceed from 

 a segment which is well developed, especially on the under- 

 side of the foot, and of which tiie lamelliform prolongation 

 between the claws forms an enq^odium. 



As an attentive perusal of the preceding pages will show, 

 Ann. & Mag. N. Hist. Ser. G. Vol. xii. 33 



