APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS. 365 
setose on the surface, whereas, the bract of Apus is always 
devoid of muscular connection, and on its surface free from 
sete. In fact, the bract of the limb of Apus appears to cor- 
respond, if with anything, in the limbs of Astacus and other 
Decapods, with branchial villi or lamelle, and not with any 
of the large divisions of the limb. The corresponding max- 
illipede of a young Sergestes (JX) and of Paleemonetes (X/J/) 
at the mysis-stage of development exhibit points of agreement 
with the Apus limb, which confirm the identifications just 
made in the case of Astacus. In Sergestes a subapical lobe 
(p) is present, whilst the resemblance of the Paleemonetes 
limb (XJJJ) to the young thoracic foot of Apus (XV/) is 
extraordinarily close. The flabellum in the two cases and 
the terminal endites 6 and 5 have practically identical form 
and relations respectively. 
If we now take the third maxillipede of Astacus (VJ/) 
there is no difficulty in recognising the corresponding 
parts in it and the various appendages already noticed. 
In this appendage we have fully and clearly developed 
the apophyses which are, uniformly by modern writers, 
termed internal ramus or endopodite (5, VII); external 
ramus or exopodite (6, VII), and accessory ramus or 
epipodite (F, VJJ). 
Accordingly it is now obvious that the endopodite of the 
Astacus maxillipede is the homologue of the endite 5 of the 
Apus limb, its exopodite is homologous with endite 6 of the 
Apus limb, and its epipodite is homologous with the flabel- 
lum of the Apus limb. This identification agrees with that 
arrived at in regard to the endopodite and exopodite of the 
antenna of Astacus as compared to the Apus limb through 
the intermediary of the Nauplius biramose appendage, and 
accordingly, it may be convenient to speak of the flabellum 
of the Phyllopod limb as the epipodite, the terminal endite 
as the exopodite, and the fifth endite as the endopodite. The 
two basal joints of the Astacus maxillipede constitute the 
corm, and are usually termed the protopodite collectively, the 
proximal joint being the “ coxopodite ” (VIZ 1, 2), and the 
distal the ‘‘ basipodite ” (VII 3, 4). These two pieces agree 
precisely in their relations to endites and exites with the two 
segments of the corm of the second thoracic foot of Apus 
(Pl. XX, fig. 8, Aw, Azx*); on the other hand, the first 
thoracic foot of Apus (Pl. XX, fig. 7), shows each of the two 
pieces of the axis or corm in a further state of division. The 
four pieces of the corm of this limb have no similarly four- 
fold representative in the protopodite of any Decapod ; and 
the two proximal together represent the coxopodite, and the 
