210 



HANDBOOK OF INVERTEBRATE ZOOLOGY. 



Ti, Notice the two pairs of swimming feet (Figs. 105 

 and 106, iirvp^^ mp^), wliich project beyond the lower edge 

 of the carapace, and end in long swimming hairs. They 

 are the first and second pairs of maxillipeds, which are 

 organs of locomotion in the zoea, but mouth-parts in the 

 a,dult crab. 



^. Notice the antennules (Fig. 

 105, A)y and the antennae {An) pro- 

 jecting downwards behind the ros- 

 trum. They vary greatly in size in 

 different zoeas, and may be much 

 longer or much shorter than they are 

 in Callinectes. 



j. A large rounded Idbrum (Fig. 

 105, L) lies on the middle line of 

 the ventral surface, and between it 

 and the bases of the maxillipeds are 

 the mandibles, and two pairs of 

 maxilloe. 



Fig. 107. — Antennule and antenna of the 

 zoea shown in Fig. 105. (Drawn by W. K. 

 Brooks from a sketch by E. B. Wilson.) 



A. Antennule. An. Antenna. 



Fig. 107. 



k. Make a sketch of the zoea showing these points. 



I. Place a zoea on a glass slide in a drop of sea-water, 

 and laying a piece of paper near it to support the cover- 

 glass, gently cover it, and examine it with a higher pbwer, 

 noticing : — 



1. The antennules (Fig. 107, A). Each consists of a 

 short swollen basal joint, which carries two long sensory 

 hairs, and, in Callinectes, a third much shorter hair. 

 Notice that the two long hairs do not taper, but are uni- 

 formly thick from base to tip. 



