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 antermule 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 Ln 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 

 are directed forward, and 

 their originally anterior 

 faces have become their up- 

 per sides. (PI. xxxm.) 

 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 



Fig. 2. — I/eft second pereiopod of first larva of lobster, showing the primitive di- 

 vided form of the limb, with successive segments orpodomeres of protopodite {pro, 

 segments 1-2), and permanent inner branch or endopodite (End, 3-7). Ex, decid- 

 uous swimming branch or exopodite; Ep, epipodite or gill separator, with its gill 

 or podobranch (pbr). 



