of the Fishery Board for Scotland. 



145 



the little rounded joint bearing the single hair is now the fourth, instead 

 of third as in the Megalops, and also in another fiist young form. In 

 Figs 21 and 23 the antennae of the right and left sides of a first young 

 stage specimen are shown. In Fig. 23, however, the first two joints are 

 not given. The antenna of the right side is incompletely developed. 

 This may be in consequence of an injury, and the part may be in process 

 of reproduction. The antenna of the left side was 9 -jointed, but had 

 not the two long hairs on the seventh joint. 



The first joint shows a recess in its outer surface, and behind it a 

 tooth. A few more hairs are found on the first joint, and some of 

 these are ciliated. 



The first three joints have scattered over their surfaces minute 

 " needle-point " cilia, which are arranged singly or in groups of 2, 3, 

 or 4. These cilia are an important character in the first young stage. 



Mandible, mn, PI. vii. 



I. (Fig. 8). The Mandible is 1 -jointed. It consists of two distinct 

 parts, a cutting edge (e), and a massive crushing crown (cr). Alongside 

 the crown a large triangular tooth (t) rises in line with the cutting edge. 

 There is no palp. Spence Bate drew attention to the resemblance 

 between the mandible of the Zoea of Carcinus and that of an amphipod. 



II. (Fig. 24), III. (Fig. 22), IV. (Fig. 9). In the remaining Zoea 

 stages the mandible retains the characters of the I. Zoea. 



Megalops (Fig. 26). The mandible is now very much changed. The 

 cutting edge ends in a prominent stout angle. It has a rounded cutting 

 edge and a 3-jointed palp. The palp (Fig. 26, h) has on its end joint a 

 series of seven stout short hairs, which are provided with stiff cilia 

 (Fig. 27). The palp arises from the upper side of the mandible. 



1. (Fig. 10.) The inferior corner of the cutting edge is turned up. 

 The hairs on the palp have increased in number. Otherwise the 

 mandible is little changed. The figure shows the upper surface. 



Labrum^ Ir. Labium, lb. Plate vii. 



The labrum of I. Zoea is shown in Fig. 33 ; the labium is seen in 

 Fig. 25. 



First Maxilla, Im, Plates vii. and viii. 



I. (Fig. 14). The first maxilla has a 2 -jointed protopodite. The 

 inner edge of each lobe is furnished with toothed spines. Rising from 

 the second joint there is a 2 -jointed palp. 



The palp bears at its extremity six stiff blunt hairs, one of which has 

 on its proximal half a few long cilia. Of the others one or two are 

 minutely serrated (Fig. 34, a). There is a similar hair on the first joint 

 of the palp. 



The spines on the protopodite lobes are strong, with large teeth or 

 stout lanceolate cilia. On the upper lobe there are five spines ; on the 

 lower lobe there are seven. The latter are provided with long lanceolate 

 cilia, as are also certain of the spines of the upper lobe. Figs. 31, 32, 

 and 34, b, c, are spines of the protopodite lobes. The spines are similar 

 to those found on the first maxilla of the Zoea of Crangon vulgaris. 



On the lower edge of the upper lobe there were three groups of cilia. 

 They were not noticed in the other Zoea stages. 



II. (Fig. 37). The first maxilla has gained a number of spines, 

 eight being present on each lobe. On the outer edge of the upper 



K 



