of the Fishery Board for Scotland. 153 
IIT. (Fig. 74). The buds have grown rapidly. There is an indica- 
tion of a basal joint being segmented off on the chela. In one example 
also the dactylopodite was segmented off on the chela. 
IV. (Figs. 67, 79, and 82). The pereiopods are now segmented. The 
first joint consists of the proximal part, i.e. the future pleuron. The 
jointing is distal to the gills in the first three pereiopods (Figs. 67 and 
79). Beyond that there are five segments. The pereiopod is divided 
into six joints, in which the first becomes the pleuron (ap, 2b.), and the 
remaining five joints form the adult pereiopod. The complete segmen- 
tage into six joints was not found in every IV. Zoéa, e.g. in Fig. 82 only 
five joints were made out. 
Mecauops (Figs. 89, 90, 93, 95, 105, 106). In this stage all the 
pereiopods are functional. The 6-jointed state of the previous stage 1s 
now replaced by a 7-jointed condition, in which the first joint is the 
pleuron, and the remaining six form the walking limb, the joints being 
the coxopodite (cox), basi-ischiopodite (b-isch), meropodite (mer), carpo- 
podite (carp), propodite (prop), and dactylopodite (dact), Fig. 99. The 
basi-ischiopodite is so named from the view that it represents the union 
of the basiopodite and ischiopodite joints of the walking limb of the 
Macrouran.* It is interesting that no such union is shown in its 
development. Instead of any reduction taking place in the number of 
joints, the resulting number is the maximum amount of segmentation 
through which the limb passes. It is probable that the basi-ischiopodite 
joint is segmented off from the third joint in the IV. Zoéa (i.¢., counting 
the pleuron as the first joint). 
The pereiopods in the Megalops have certain characters which belong 
to this stage and which vanish in the next stage. These consist in a 
large hook on the distal part of the basi-ischiopodite of the chela, short 
toothed spines on the dactylopodite (and propodite) of the second, third, 
and fourth pereiopods, and the long curved spines which so well 
characterise the dactylopodite of the fifth pereiopod. 
The drawings of the 1-5 pereiopods—viz. Figs. 106, 95, 93, 89, and 
105 respectively—do not show the whole limb, but simply that part distal 
to the fracture plane, which occupies the same position as in the adult, 
(on the proximal part of the basi-ischiopodite). The differences between 
the limbs are found on these parts. Fig. 90, however, shows the com- 
plete fifth pereiopod, and Fig. 101 is an enlarged drawing of the 
coxopodite and basi-ischiopodite joints. There is little difference to 
remark between the coxopodites of the pereiopods except that of size 
(Fig. 149, Pl. xii.). In the preserved specimen the limb breaks off 
readily at the fracture plane: this is especially the case where the 
Megalops or young crab has been killed in the preserving fluid. 
All the limbs are well furnished with smooth hairs. The coxopodites 
have a few hairs, which are usually plumose (Fig. 101). 
lsv Pereztorop (Fig. 106). The first pereiopod is a functional chela. 
The basi-ischiopodite joint is expanded at its distal inner border into a 
strong curved hollow hook. Spread over the different joints are 
the short hairs shown in the sketch; the propodite and dactylopodite 
are profusely supplied with these (Fig. 109). Along either side of the 
‘‘knife-blades” are three (or two) of the short stiff curved hairs which 
were found in a similar situation on the chela of the VI. (Megalops) 
stage of Crangon vulgaris. The knife-blades are crossed by what 
appear to be little tubes; a bundle of these is seen in the claw termina- 
tion of each jaw. In connection with similar tubes found in the chela 
of Crangon, it was suggested that possibly by these a lubricant of somo 
* Léon Fredericq. 
