352 PROFESSOR E, RAY LANKESTER. 
usually the rudimentary bract is absent in the full-grown 
condition, but I have, on the contrary, never failed to find 
it. Claus (loc. cit.) likewise figures this appendage from a 
larval Apus, and correctly identifies its component parts and 
the rudimentary bract which does not enter into the compo- 
sition of the egg box. Huxley also (loc. cit.) describes the 
adult oostegopod, but without mentioning the rudimentary 
bract ; he, however, identifies the movable lid as the flabellum 
(his “‘ exopodite’’), and the fixed cup-like portion as an out- 
growth of the axis (his ‘‘ endopodite”). Gerstaecker, how- 
ever, having missed the rudimentary bract (which may or 
may not be present in the Apus productus figured by him), 
proceeds to identify the fixed portion of the egg box with the 
flabellum (his “lamelliform branchia”), and the movable 
lid with the bract (his vesicular (blasenformiger) branchia). 
Gerstaecker’s being the latest study and identification of 
these organs, it is of some importance to point out emphati- 
cally that the movable lid is not the bract, but the flabellum, 
whilst the bract exists in Apus cancriformis in a rudimentary 
condition in the adult appendage, as exhibited in Pl. XX, 
fig. 10. 
I have not had an opportunity of examining, in the living 
state, the exact disposition of the muscles and the mechanism 
of the egg box, but I must point out that the cireular 
muscles described by Zaddach have no existence. The 
modified flabellum alone has a muscular supply, which does 
not differ from that of the other flabella. 
Appendages next in front of the oostegopods.—A marked 
difference in the proportions of the outgrowths of the limbs 
in front of the oostegopods is observed, as compared with 
those posterior to those specialised appendages. 
In Pl. XX, fig. 9, the ninth of the thoracic (pregenital) 
series of foot-like appendages is represented. Whilst the 
gnathobase (endite 1) and the four next endites (2, 3, 4, 5) 
present no peculiarity for notice, the sixth endite is remark- 
able for its firmly chitinised walls, its denticulate ventral 
margin and its ex-axial lobe, which projects beyond the point 
at which the endite is articulated to the axis, and works in 
a notch of that portion of the limb. 
The subapical lobe (p) is well developed and acutely an- 
gular. The flabellum is more elongated than in the 
abdominal (post-genital) appendages, being developed on 
either side of its point of attachment to the axis, instead of 
being quadrate or oblong. The two regions of the flabellum 
may conveniently be spoken of as “the distal lobe’ (that 
apexwards in relation to the muscular attachment), and 
