STUDIES ON THE AKACHNID ENTOSTEKNITE. 243 



Bernard's recognition of the homologies existing between the 

 ports of this plate in different orders, homologies which are, 

 at all events, fairly obvious in the case of the Pedipalpi and 

 Aranete. To quote his own words (4), "In the Spiders . . . 

 the entosternite consists of four pairs of apodemes which 

 meet in the centre, the second pair of which correspond with 

 the entosternite of Galeodes and Scorpio, whilst the first 

 pair is perhaps represented in Galeodes by the fibrous plate 

 above described. In Phrynus the entosternite is difficult to 

 unravel ; it may perhaps represent only the first pair of 

 apodemes of the spiders with secondnr}^ attachment of dorso- 

 ventral muscles. In Thelyphoiius we have a long 

 fenestrated entosternite which may correspond with that of 

 the Spiders ; the component apodemes not, however^ meeting 

 in a point." 



I venture to think that the new facts and theories concernins- 

 the entosternite of the Pedipalpi and Aranete put forward in 

 this essay will show that the homologies are by no means 

 so vague and difficult to unravel as the passage quoted would 

 lead one to suppose. 



Schimkewitsch (10) terms the apophysis that rises from 

 the upper side of the anterior bar in Thelyphonus a dorso- 

 ventral outgrowth, and those numbered Ifg., '2fg., ofg., and 4tg. 

 in fig. 2, PI, 13, as lateral outgrowths, homologising the latter 

 apparently with the lateral crest, and the former with one of the 

 dorsal apophyses in the Araneas. I cannot think this interpre- 

 tation correct in view of what obtains in the entosternite of 

 Phrynus. The Pedipalpi and the Aranete are so very closely 

 related that the conclusion as to the homology between the 

 apophyses of the entosternite appears to me inescapable. 



The entosternite of Limulus forcibly recalls that of 

 Thelyphonus. The anterior l)ars correspond in the two. 

 Following these in L. polyphemus come the two long, 

 slender apoj)hyses running out towards the bases of the third 

 and fourth appendages, and representing, I believe, the dorsal 

 portions of the tergo-sternal muscles of the corresponding 

 somites. A comparison between these and the second and 



