226 
bulletin of the bureau of fisheries. 
in a few hours by the second antennae, both arising as simple buds, and all three pairs 
become concentrated about the mouth in the early egg nauplius stage, which is thus 
reached at the tenth or eleventh day. Both pairs of antennae are then distinctly divided 
at the tips, as if about to branch, but the second pair only becomes biramous, the 
first remaining as single constricted stalks up to near the end of embryonic life. 
When the larva emerges, what is to be the inner and slenderer branch of this 
appendage is seen arising as 
a small bud from the base 
of what becomes the outer 
and thicker flagellum (fig. 
34). The inner branch of 
the antennule is therefore 
probably not homologous 
with an endopodite. The 
outer branch develops its 
club - shaped ‘ ‘ olfactory ’ ’ 
setae in the second larval 
stage, and remains very 
short and stout up to the 
fourth or fifth stages, when 
it rapidly lengthens. 
It should be noticed 
that the lower or sternal 
part of the head faces for- 
ward instead of downward, 
as a result of cephalic flexure 
which arises in the course 
of embryonic development; 
in consequence of this the 
anterior sterna are bent up- 
ward through nearly a right 
angle, so that the eyestalks 
and both pairs of antennae 
Fig. 2.— Left second pereiopod of first larva of lobster, showing the primitive di- directed forward, and 
vided form of the limb, with successive segments or podomeres of protopodite (/>ro, . . . „ 
segments 1-2), and permanent inner branch or endopodite (End, 3-7). Er, decid- their Originally antenor 
uous swimming branch or exopodite; Ep, epipodite or gill separator, with its gill faceS have beCOme their Up- 
or podobranch (^6r). -.4 ' /r>, s 
per sides. (PI. xxxiii.) 
Assuming that neither the eyes nor antennules are metameric appendages, and 
that the telson is not a true somite, the body would consist of a prostomium bearing 
the two pairs of articulated processes named, eighteen metameres, and a terminal telson, 
the first four somites being fused with the prostomium to form the head, with appen- 
dicular antennae, mandibles, and maxillae. 
Since it will be necessary to examine the swimmerets, the compound eyes, and 
statocysts in relation to other organs, the account which immediately follows will be 
