TRACHEATA. 



361 



the ambulatory feet. The abdomen is bent forwards so as to reach 

 almost to tlie pedipalpi. In the later stages (tig. 198 C) the adult form 



FIG. 197. SEGMENTATION AND FORMATION OF THE BLASTODEBM IN CHELIFEB. 



(After Metschuikoff.) 



In A the ovum is divided into a number of separate segments. In B a number of 

 small cells have appeared (bl) which form a blastoderm enveloping the large yolk 

 spheres. In C the blastoderm has become divided into two layers. 



is gradually attained. The enormous upper lip persists for some time, 

 but subsequently atrophies and is replaced by a normal labrum. The 

 appendages behind the ambulatory feet atrophy, and the tail is gradually 

 bent back into its final position. The segmentation and the gradual 

 growth of the limbs do not call for special description, and the formation 

 of the organs, so far as is known, agrees with other types. 



The segmentation of Chthonius is apparently similar to that of Chelifer 

 (Stecker, No. 437). 



Phalangidffl. Our knowledge of the development of Phalangium is 

 unfortunately confined to the later stages (Balbiani, No. 438). These stages 

 do not appear however to differ very greatly from those of true Spiders. 



Araneina. The eggs of true Spiders are either deposited in nests 

 made specially for them, or are carried about by the females. Species 

 belonging to a considerable number of genera, viz. Pholcus, Epeira, 

 Lycosa, Clubione,, Tegenaria and Agelena have been studied by 

 Claparede (No. 442), Balbiani (No. 439), Barrois (No. 441) and myself 

 (No. 440), and the close similarity between their embryos leaves but 

 little doubt that there are no great variations in development within 

 the group. 



