Fig. bS.—Astaciis fluviatilis.— Surface views of the earlier stages in the development of 

 the embryo, from the appearance of the blastopore (A) to the assumption of the 

 nauplius form (F) (after Reichenbach, X at)Out28). hp, blastojtore , c, carapace; fg, 

 fore-gut involution ; h, heart ; hg, hind-gut involution ; lb, labrum ; nig, medullary- 

 groove : 0, optic pit ; p, endodermal plug partly filling up the blastopore ; pc, pio- 

 cephalic processes ; ta, abdominal elevation ; ^, aiitennules ; 3, antennae U, man- 

 dibles. 



