364 PROFESSOR E, RAY LANKESTER. 
Suppose that the long endites 5 and 4 were the parts 
homologous with the external and internal ramus respec- 
tively of the Nauplius limb; but the actual fact is that the 
reduced claw-like endite 6 is the homologue of the exopodite 
of the Nauplius antenna. 
As has been pointed out above, the biramose antenna of 
the young Apus survives in the adult as a minute filamentous 
appendage, in which both endites 6 and 5 have atrophied, and 
only a portion of the axis and the small endite 1 (see 
woodcut, XV JIT) persist. 
The homologies of the parts of the appendages of some 
Malacostraca with those of Apus.—The attempt to establish 
a close correspondence between the apophyses of the appen- 
dages of the Phyllopoda and the Podophthalmata has its 
justification in the existence of the annectant form Nebalia, 
and of the Nauplius larval forms of some of the latter group. 
The foliaceous maxille and maxillipedes of such Decapods as 
Astacus also suggest a correspondence with the foliaceous 
truncal feet of Phyllopoda, which can be established in detail 
on close comparison. 
If we take the second maxilla of Astacus to begin with 
(woodcut, V) we find it to consist of an unjointed corm with 
six endites, comparable to the six endites of the abdominal 
feet of Apus (Pl. XX, fig. 11). 
The terminal endite is enlarged, and has a distal and a 
proximal lobe, as is more or less the case in the corre- 
sponding endite of the Apus limb. Two rudimentary exites 
(p in the woodcut) only are present, and in the adult are 
fused with the proximal lobe of the enlarged endite. In the 
Zoea phase of many Decapoda the enlarged endite is free 
in this region (woodcut, VJ//), and in some cases the re- 
semblance to a Phyllopod foot with suppressed flabellum and 
bract is very strong (woodcut, JX). 
Passing to the next appendage of Astacus—the first max- 
illipede (woodcut, VI)—we can count the six endites asin the 
second maxilla, the sixth being greatly changed in form; 
instead of being a simple crescentic plate, it now has the 
shape of a rod, and is polyarthrous. But this change is no 
greater than that presented by the transition from the poly- 
arthrous endites of the first thoracic limb of Apus to the 
lamelliform endites of the second and third limbs of that 
animal. A large exite is now present (/’) with a small distal 
(d), and larger proximal lobe. It corresponds with the fla- 
beilum of the Apus limb and cannot be compared to the 
bract, owing to the fact that in this and subsequent appen- 
dages it has a muscular connection at its base and is richly 
