DEVELOPMENT OP PHRYGANIDS. 579 



The upper lip is formed by a fold in the germinal band just 

 in front of the mouth; its cavity, which is lined with meso- 

 derm, opens directly into the body cavity (Pi. XXXVIa, figs. 

 9, 10, 12, 13, 14, and/, hd.). 



The antennae appear as knot-like protuberances on the 

 posterior edges of the procephalic lobes (PI. XXXVIa, fig. 10, 

 &c., at.). Here it will be seen that they are very prominent ; 

 gradually, however, they become less conspicuous, until in the 

 later stages they are scarcely to be observed at all. When, 

 however, the embryo has emerged from the chorion the 

 antennae again increase somewhat in size, although still remain- 

 ing quite small. Zaddach^s statement that a second pair, cor- 

 responding to the first pair of crustacean antennae, appears after 

 hatching, the first pair having entirely disappeared, is erroneous. 



The nervous system is primarily indicated by a shallow 

 groove, beginning at the anterior end of the body, and ex- 

 tending backwards almost to the tip of the germinal band, 

 terminating at the place where the proctodaeum is to 

 be formed. As development proceeds, the cells on each side 

 of the groove divide and give rise to faintly marked nuclei, 

 each of which contains a small deeply stained nucleolus (PI. 

 XXXVIb, figs. 12 and 13). By the increase in numbers of 

 these cells, a continuous cord is formed on each side of the 

 median furrow. This condition, however, does not last long, 

 for, on the dorsal side of these cords, deeply stained granular 

 nuclei appear (PI. XXXVIc, fig. 21, x), which finally increase 

 to such an extent as to almost take the place of the faintly 

 marked nuclei (PI. XXXVIc, fig. 23). These granular neural 

 cells at first form a single layer directly under the neural 

 cords. I at first thought them to be transformations of the 

 nuclei above them, but certain indications render it possible 

 that they were formed by division of the ectoderm cells on each 

 side of the neural cords (PL XXXVIc, fig. 21, y), for in stages 

 slightly earlier than that represented in the figure, these cells 

 were observed only at the point marked y, and appeared to 

 grow inwards towards the median line. This point, however, I 

 was not able to determine with certainty. 



