30 G. 0. Sårs. 



some places, especially in the region of the mouth. In 

 front, the ocular plate appears very sharply denned, and 

 exhibits, when seen from above, a somewhat cordiform shape, 

 with the 2 fascicles of glistening fibres very conspicuous 

 (see fig. 2). Immediately below this plate, between the 

 insertion of the antennulæ, there is a rather small rounded 

 prominence containing the simple eye. Of the compound 

 eyes, on the other hand, no traces are as yet to be detected. 

 The intestine can now be clearly traced in its whole length, 

 beiûg produced in front to a median cæcal expansion, and 

 its posterior part exhibits, during life, continual peristal- 

 tic movements. The liver-sacs are also rather distinctly 

 defined, each exhibiting 3 unequal lobules clothed with large 

 cells. The heart is very conspicuous in the living animal, 

 on account of its rapid pulsations, being located immediately 

 beneath the dorsal face of the carapace, at some distance 

 from its posterior edge. Finally, the ventral nervous cord 

 admits of being more or less distinctly traced, its posterior 

 part, lying within the metasome, exhibiting a row of 6 

 densely crowded ganglia. 



Second Calyptopis-stage. 



(PL 4, fig. 3). 



In this stage the larva has attained a length of 1.60 

 mm., and exhibits a fuller development, especially of the 

 antennulæ and of the metasome. Moreover, in this stage 

 the first indication of the compound eyes may be traced in 

 the form of an irregular patch of a light red pigment 

 occurring on each side of the ocular plate in front of the 

 the luminous fibres. The antennulæ now show themselves 

 to be composed of the same parts as in the adult animal, 

 though the peduncle is still rather clumsy, and the 2 flagella 



