TRACHEATA. 



441 



next four are provided with provisional appendages ; while the 

 last six are without appendages. The further features of this 

 stage which deserve notice are (i) the appearance of a shallow 

 depression (st) the rudiment of the stomodseum between the 

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



FlG. 2OO. FOUR STAGES IN THE DEVELOPMENT OK 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 chelicera; 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. stomodteum between the two proe-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. stomodaeum ; ch. chelicerrc ; on their inner side is seen 

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



raised areas on the inner side of the six anterior appendage- 

 bearing segments. These are the rudiments of the ventral 

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



