252 v.. f. POCOOK. 



inid-regiou of tlie prosoma^ as 1 uiii inclined to believe, are 

 (juestious wliicli must for blie present be left unsettled. The 

 evidence we possess that at least the dorsal and ventral 

 processes of the entosternite in the spiders are modified 

 muscular tendons seems to make it unnecessary to look else- 

 where for the source of the formation of the entire plate. 



This conception, of the origin of the entosternite from 

 muscular and connective tissue differs entirely from that held 

 by Bernard (3, 4), who would derive this plate in all 

 terrestrial Arachnids from integumental apodemes anil 

 seguiental constrictions. It may be inferred from what he 

 says about the entosternite of My gale that he regards its 

 four pairs of dorsal and ventral processes as the remains 

 of integumental infoldings marking the line of union of 

 the originally separated tergal and sternal elements of the 

 prosoma.' He adds, " The chape of the whole i'used mass 

 has been, no doubt, much altered by the action of muscles, 

 but its essential nature as a fusion of metamerically recurrent 

 apodemes cannot be mistaken" (3, p. 20). In his paper on the 

 morphology of the Galeodidtc (4, p. 327) he says that in the 

 Pedipalpi and Araneas "four pairs of dorso-ventral muscles 

 have been retained, more or less modified, as the dorsal 

 attachments of the entosternite, and ai'e now largely fibrous; 

 they suspend the entosternite and separate the alimentary 

 diverticula in the typical manner." Hence may be inferred 

 the admission that part at all events of the dorsal processes 

 ot" the entosternite have been derived from dorso-ventral 

 muscles. If part, why not the whole of the dorsal process ? 

 And if the dorsal process represents the part of the nniscle 

 above the entosternite, what reason is there for refusing to 



^ licniiuil btaics that the oiij^inal distinctucbs of the teri,'a of llie cara|iace 

 ill the Arauca; is shown by Uic furrows on il-s dorsal surface. These furrows 

 are in reaUly Uic external iiuiicalioiis of fhe radial arraiigeiiicnt, of the t,n'i.'<it 

 dorsal appendicular muscles, and mark the lines of attaclimeiit of the muscles 

 rising dorsally between them from the entosternite. If the grooves indicated 

 the union of tergal plates, such plates sliould be more clearly defined in the 

 enibi yo, but so far as I am aware the carapace of spiders at no |)eriod of its 

 development shows division into separated tergal plates. 



