DEVELOPMENT OF THE EXTERNAL FORM OF THE BODY. 



55 



is specially marked in Epeira. The embryo itself, with its long 

 abdomen, the anterior segments of which are broad, while the 

 posterior are narrow, bears, if we may trust Barrois' account, a 

 decided resemblance to the Scorpiones. 



Barrois gives such distinct figures of this stage, both in dorsal aspect and in 

 profile, that we should not hesitate to accept his description were it not denied 

 by other authors that the dorsal segmentation described by him is actually 

 present (Schimkewitsch, Nos. 12, b, and 72). 



The rich segmentation of the abdomen, ten or even twelve seg- 

 ments being sometimes found, gives the embryo, before flexure- 

 reversal (or perhaps sometimes, as in Epeira, shortly after that 

 process) an appearance quite unlike that of an Araneid. A change, 



e^. 



^ 



Ae&. 



Fio. 30. — Older embryos of Agalena iiacvia, A, showing the commencement of the flexure- 

 reversal. D, having completed the flexure-reversal, and near hatching (after Locv). The 

 embryo in A is viewed somewhat obliquely. ab 1 -db e the first abdominal segments, four of 

 which cany the provisional limbs; d, yolk; cli, chelieerae ; ped, pedipalps; p, the four 

 ambulatory limbs of the right side; 11, cephalic lobe; si, caudal lobe; sp, spinning 

 mammillae (provisional abdominal limbs). 



however, is brought about through the great development of tin- 

 anterior abdominal segments, especially of those which carry the 

 rudiments of limbs, this being accompanied by the reduction of the 

 other segments. This process can be observed in Agalena at an 

 early stage of flexure-reversal. According to Loct, the anterior 

 abdominal segments grow with unusual rapidity towards the dorsal 

 side. Fig. 30 ^4, which illustrates the stage under consideration, 

 represents the postero-lateral aspect of the embryo, so that the 

 anterior abdominal segments can be recognised at each side growing 

 up dorsally. Between them lies the bent caudal lobe (si), and the 

 yolk-sac (d) already appears on the ventral side in this region. The 



