of the Fishery Board for Scotland. 



155 



escaped notice may be present. The fifth pereiopod is the shortest ; the 

 propodite joint is shorter than in the second, third, and fourth limbs. 

 The hairs on the dactylopodite are longer in the former than in the 

 latter. 



As in the previous stage, only the part of the limb distal to the 

 fracture plane is shown in most cases. Fig. 126 shows the complete 

 fifth pereiopod, and Figs. 123 and 140 show two views of the coxopodite 

 and proximal part of the basi-ischiopodite of the chela. Fig. 114 

 represents an enlarged drawing of the coxopodite and basi-ischiopodite 

 of the fifth pereiopod. 



Beanchi^, br. 



The branchiie, as Glaus* pointed out, are all appendages of the liinb, 

 and the positions which they occupy on the developing limb determine 

 them as the future podobranchs, arthrobranchs, or pleurobranchs. In 

 this connection, Claus wrote as follows : — " An jener entsprechen die 

 drei iibereinander sprossenden Kiemenknospen jedes Somiten gar nicht 

 dem sinne der Huxley'schen Nomenclatur, sondern gehbren dem langges- 

 treckten Basalglied an, von dem sich erst nachher der distale Theil 

 als Coxalglied absetzt, wahrend der proximale mehr oder minder weit 

 in die Wandung des Rumpfes aufgenommen wird."* 



Compare also, in this connection, E. L. Bouvier : — " Sur le developpe- 

 ment embryonnaire des Galatheides du genre Diptychus." Comptes 

 Rendus Acad. Sc. Paris, cxiv (1892). 



The branchiae are not functional in the Zoea stages. During the 

 Zoea period they are developing, and in the Megalops certain of them 

 are functional. These are the two arthrobranchs attached to the chela 

 and the two pleurobranchs of the second and third pereiopods ; 

 they are completely cut up into lobes. The other gills — viz., those of 

 the second and third maxillipedes— are not yet lobed. 



I. The rudiments of most of the gills can be seen in the I. Zoea, 

 they are all parts of appendages. The future branchia3 of the third 

 maxilhpede and of the pereiopods are all hollow outgrowths of he 

 hollow rudiments of these appendages. In the I. Zoea, then, we have 

 the beginnings of the future arthrobranchs and pleurobranchs. On the 

 third maxillipede and the chela are the buds of arthrobranchs, and on the 

 second and third pereiopods buds of pleurobranchs. In Fig. 69, PI. ix., 

 a drawing of these is given. It is there seen that the gills of the second 

 and third pereiopods br'") arise from the basal part of the limb- 

 bud, while the large gill-rudiments of the chela (W) and of the third 

 maxillipede (br) arise farther up the limb-bud. In the former couple we 

 have pleurobranchs, in the second arthrobranchs. The pleuron of the 

 adult is formed out of the basal part of the limb ; and this basal portion 

 includes the gill in one case, and ends just at the gill in the other, so 

 that the gill occupies a position between the limb and its basal part 

 (pleuron). 



The large swellings of the third maxillipede and of the chela become 

 each a pair of arthrobranchs. 



In one view of the second maxillipede (Fig. 85) a process of the first 

 protopodite joint was seen (br ?). It may be the rudiment either of a 

 gill or an epipodite, or what is not unlikely, of both. 



II. (Figs. 84 and 73). In the II. Zoea, on the third maxillipede there 

 are now three swellings — the top one, an epipodite, the lower two, gills. 



The gill of the chela is still single. 



* Claus, "Neue Beitriige zur Morphologie der Cnistaceen." Arb. a. d. Zool. Inslit. 

 Wien, T. vi., 1886. 6Taf., p. 1. 



