Limbs and Mouth-parts of Crustaceans and Insects. 433 
tion may be best compared to the paragnathi of Crustacea, 
although a homologization with the latter structures may well 
appear to be out of the question ”) can belong to the maxillulee 
is a question which must receive further elucidation from 
future embryological investigations. 
49. In different Insects we can (with especial ease in all 
Cicadaria in the case of all legs, with exception of the last 
pair in Fulgoride) 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 maxille (§$28, 29, and 
25). 
50. 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 may make the following statement :— 
In the Collembola we meet with a structure which agrees in 
the closest manner with the condition discussed in § 21 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 which there proceeds a long and powerful 
claw (with a somewhat large cheliform process on each side), 
while to the underside of the segment another smaller claw is 
articulated. Jf£ we now start trom my morphological interpre- 
tation in the case of the Myside (§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 Tullberg). In Japye solifugus the 
lower claw has passed up on to the 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 toot, and of which the lamelliform prolongation 
between the claws forms an empodium. 
As an attentive perusal of the preceding pages will show, 
Ann. & Mag. N. Hist. Ser. 6. Vol. xii. 33 
