468 ROBERT GUENEY. 



1. Length of rostrum 



2. „ dorsal spine 



3. Tip to tip of spines 



4. Length of body . 



5. ,, thorax 



6. Eatio of 4 to 3, 1 : 1-67. 



It will be seen that though the absolute length of the 

 spines is much greater at this stage than in the preceding 

 one, the ratio between the total length and the total length 

 of the body has increased only by •01. 



The more important differences between the zotea at this 

 period and that of the preceding one are the following: — In 

 the second antenna the flagellum, which is barely indicated 

 in the first stage, has grown out to nearly the length of the 

 exopodite (spina mobilis) . The exopodite and inner spinous 

 prolongation of the stem are unchanged. 



The maxillffi have changed but little in form, but bear 

 more setae. The scaphognathite of the second maxilla (fig. 

 10) has now nine setiB along its inner margin, and there are 

 three terminal seta) instead of the single one of the preceding 

 stage. 



The first two maxillipedcs are unchanged, except that the 

 exopodite bears distally six ciliated sette instead of four. 

 The remaining thoracic legs are more distinctly developed, 

 and there are traces of six gills on each side, i. c. those of 

 the third maxillipedes and three succeeding limbs. 



In the abdomen the pleopods are marked out as knobs on 

 each segment except the first, which remains limbless 

 throughout the larval development. Tlie third, fourth, and 

 fifth segments are produced into a short spinous jn-ocess on 

 each side. The sixth segment is separated from i\\v telsoii. 

 In the latter (fig. 4) the nunilKM- of internal sehe is increased 

 by one or even two pairs, so that there arc either six or seven 

 on each side altogether. 



