468 SCHIZOPODA. 



two frontal papillae very similar to those already described in the Phyllopod 

 larvae. Rudiments of the compound eyes make their appearance, and 

 though no new appendages are added, those already present undergo further 

 differentiations. They remain however very simple ; the maxillipeds 

 especially are very short and resemble somewhat Phyllopod appendages. 



Up to this stage the tail has remained rudimentary and short, but 

 after a further ecdysis (Claus) it grows greatly in length. At the same 

 time the cephalo-thoracic shield acquires a short spine directed backwards. 

 The larva is now in a condition to which Claus has given the name of 

 Protozoasa (fig. 213 A). 



Very shortly afterwards the region immediately following the segments 

 already formed becomes indistinctly segmented, while the tail is still with- 

 out a trace of segmentation. The region of the thorax proper soon be- 

 comes distinctly divided into seven very short segments, while at the same 

 time the now elongated caudal region has become divided into its normal 

 number of segments (fig. 213 B). By this stage the larva has become 



FIG. 213. LARVAE OF EUPHAUSIA. (After Claus.) From the side. 



A. Protozorea larva. B. Zonea larva. 



mx'. and tux", maxillre I and 2 ; mxp^. maxilliped r. 



a true Zoaea though differing from the normal Zoaea in the fact that 

 the thoracic region is segmented, and in the absence of a second pair of 

 maxillipeds. 



The adult characters are very gradually acquired in a series of suc- 

 cessive moults ; the later development of Euphausia resembling in this 

 respect that of the Phyllopods. On the other hand Euphausia differs from 

 that group in the fact that the abdominal (caudal) and thoracic appendages 

 develop as two independent series from before backwards, of which the 

 abdominal series is the earliest to attain maturity. 



