of the Fishery Board for Scotland. 



147 



II. (Fig. 39). The number of spines found on the second maxilla 

 drawn was (5 -f 3 : 4 -f 5) : (3 + 3). 



The scaphognathite had nine plumose setae. 



III. (Fig. 61). The spine formula found in this example was (5 + 3 : 

 5 + 5): (4 + 3). 



There were 18 plumose setae on the scaphognathite. 



IV. (Figs. 40 and 55). The spine formula was (5 + 3 : 5 + 5) : (4 + 3). 

 In III. and IV. Zoese then there is one spine more than in 



I. Zoea. 



The scaphognathite bore 24 setae. 



Megalops (Fig. 46). While the general form remains similar, the 

 second maxilla has changed greatly in the proportions of its several 

 parts. The scaphognathite, which during the Zoea stages was rapidly 

 growing larger, constitutes now the greater part of the appendage. 

 The prominent spines of the Zoea are now replaced by short smooth 

 stiff hairs. 



The 2-jointed structure of the second maxilla is still evident. The 

 large top lobe has become differentiated into two parts, the upper of 

 which is a conical process devoid of hairs, the other a bifid lobe bearing 

 the short smooth hairs. The lower lobe is more deeply cleft ; on its 

 upper half it bears two short smooth hairs, and on its lower, four hairs, 

 one of which is provided with several long cilia, while a second has one 

 or two serrations. 



The numbers of hairs on the endognath are as follows : (0 : 3 -f- 3 : 3 + 

 4) : (2 : 2 + 2). 



The scaphognathite bears 39 short plumose setae. 



On the surface of the scaphognathite there are three little hairs, and 

 on the middle lobe of the endognath, two similar hairs. 



1. (Fig. 59). The top division of the endognath now bears a single 

 stiff hair at the middle of its length. The hair arrangement is (1 : 2 -\- 

 4 : 6) : (3 4- 4). 



Of the four hairs on the bottom part of the lower lobe, three are 

 ciliated. 



The middle portion of the endognath is now segmented off .from the 

 rest of the appendage. 



The number of short plumose setae fringing the scaphognathite is 

 largely increased. On its surface a few short hairs were noticed. 



The Maxillipedes, mp, Plates viii., ix.. x. 



In the Zoea two maxillipedes only are functional, viz. the first and 

 second pairs. Thoy act as feeding organs, and also through the action 

 of their seta-bearing exopodites, serve as the principal organs of locomo- 

 tion. The third maxillipede is not fully developed until the Megalops 

 stage. 



Spence Bate stated that " at the base of these two last pairs of 

 appendages [2nd and 3rd maxillipedes] the germ of the future branchiae 

 may be distinguished." 



When the first and second maxillipedes are examined in situ the 

 protopodite appears to consist of three joints (fig. 76). This, in view of 

 Hansen's* theory of the 3-jointed protopodite, is of some moment. Two 

 of the joints — viz., the long joint and the short one proximal to it — 

 are distinct. The "joint" connecting the latter to the thorax is 

 tapered, and it is an open question whether it is really a joint of equal 



* Hansen — '* A Contribution to the Morphology of the Limbs and Mouth-parts of 

 Crustaceans and Insects," The Annals and Magazine of Natural History VI.), vol. xii 

 1893, p. 417. 



