TRACE EAT A. 



365 



of as having a dorsal flexure. By the time that this stage is reached 

 (fig. 200 C; the full number of segments and appendages has become 

 established. There are in all sixteen segments (including the caudal 

 lobe). The first six of these bear the permanent appendages of 

 the adult ; the next four are provided with provisional append- 

 ages ; while the last six are without appendages. The further 

 features of this stage which deserve notice are (1) the appearance 

 of a shallow depression (st) the rudiment of the stomoda3um 

 between the hinder part of the two procephalic lobes; (2) the 

 appearance of raised areas on the inner side of the six anterior 

 appendage-bearing segments. These are the rudiments of the ven- 

 tral ganglia. It deserves to be especially noted that the segment of 

 the chelicerse, like the succeeding segments, is provided with ganglia; 

 and that the ganglia of the chelicerse are quite distinct from the 



FIG. 200. Form STAGES IN THE DEVELOPMENT OF AGELENA LABYRINTHICA. 



A. Stage when the ventral plate is very imperfectly differentiated, pr.c. primitive 

 cumulus. 



B. Ovum viewed from the side when the ventral plate has become divided into six 

 segments. ch. segment of chelicerte imperfectly separated from procephalic lobe; 

 pd. segment of pedipalpi. 



C. Ventral plate ideally unrolled after the full number of segments and appendages 

 are established. st. stomodaeum between the two prs-oral lobes. Behind the six 

 pairs of permanent appendages are seen four pairs of provisional appendages. 



D and E. Two views of an embryo at the same stage. D ideally unrolled, E seen 

 from the side. st. stomodseum ; ch. cheliceree ; on their inner side is seen the 

 ganglion belonging to them. pd. pedipalpi; pr .p. provisional appendages. 



