SEA-FISHERIES LABORATORY. 273 



crotchets, the smaller number being present in the first 

 three or four neuropodia. In the branchiate Lytham 

 specimen 3'9 mm. long, the crotchets are rather more 

 numerous, there being eight or nine in many of the 

 neuropodia. The crotchets of post-larval stages differ 

 from those of adults in the relatively large size of the 

 teeth, and in the angle which the rostrum makes with 

 the shaft. In post-larval crotchets the rostrum is approxi- 

 mately at right angles to the shaft, while in older speci- 

 mens it makes a much greater angle, in large specimens 

 as much as 130 degrees (cf. figs. 15, 18). 



As stated above, there are no gills in any of the seventeen 

 post-larval stages examined, except one. This one is 

 3 - 9 mm. long, and the thirteen pairs of gills are present, 

 and all except the first two are branched. The largest 

 gills are behind the middle of the series, and this is pro- 

 bably the region where the gills are first formed. In 

 other specimens no gills are indicated, but in the living 

 specimen 4'6 mm. long, immediately behind the notopodia 

 of the penultimate aud the two or three preceding chseti- 

 gerous segments, the blood-vessels form a well-marked 

 loop, as if preparatory to the formation of a gill, and there 

 is a very slight elevation of the skin in this region. Later 

 on, as shown in the Lytham specimen, the gill becomes 

 successively a papilla, a digitiform, and then a branched 

 structure. The gill arises, therefore, as a special respira- 

 tory structure, and is not a dorsal cirrus which secondarily 

 becomes a branchia. 



The tail is very similar to that of the adult. The 

 terminal segment bears a number of circum-anal papillae, 

 each of which carries a tuft of four or five sense-hairs, 

 which project posteriorly. 



The skin is glandular. It contains numerous 

 scattered cells, each filled with yellow granules. If the 

 u 



