256 i{. I. I'OCOCK. 



Pedipalpi is the lioinologue of the "^^ (lia})hi'agm " in tlie 

 Scorpioiies and Solifugte. 



This theory of the foiniation of the diaphragm seems to me 

 scarcely more plausible if the pregenital somite, which was 

 not recognised as such when Bernard wrote, is left out of 

 consideration ;^ and the following quotation shows that I have 

 given no exaggerated rendering of iiis hypothesis. He says (4), 

 ''Between the sixth and seventh segments . . . there is in the 

 Galeodidae . . . a strong intersegmental constriction. Inter- 

 nally this constriction h:is given rise to a very striking 

 dinphragm. It forms a very com|)lete wall between the 

 interior of the cephalothorax and that of the abdomen, and 

 is pierced by the dorsiil vessel, the alimontar}' canal, the 

 nerve-cords, and the tracheae. Close examination shows that 

 the diaphi-agm is due to a strong indrawing of the interseg- 

 mental membrane between the above-mentioned segments, so 

 that it is composed partly of a chitinons infolding and partly 

 of muscle-bands. It is clear that if the opposite two internal 

 faces of such a deep segmental consti-iction fuse together, they 

 form a diaphragm ; if they remain nnfnsed they form a waist. 

 In the Galeodida3 we seem to have an unspecialised an-ange- 

 nient, the intersegmental infolding being fused only in its 

 deeper parts, forming the diaphragm, while the outer parts 

 of the fold remain open, making an approach to a waist." 



Such an infolding, in its unspecialised state, must have 

 disturbed the position of the dorsal blood-vessel, forcing it 

 down towards the central axis of the body on to the alimen- 

 tary canal ; but, as a matter of fact, the blood-vessel and 

 alimentary canal show no trace of any disturbance of their 

 primitive positions, the former perforating the diaphragm 

 iiigh u]) beneath the dorsal integument, the latter traversing 

 its centre, while below, in lin(^, is seen the canal for the nerve- 



' PxTiuiid lias pointed out, to me that liis njj;in-e of tlie seelioii of tiie 

 "waist" of a Sjiider published on j)!. xxxiii, fig. fi, of liis paper " On tiie 

 Morpliolotry of the Galeodidrc," sliows llie presence of a pair of dorso- 

 ventral muscles, and tlins confirms tlie view that the waist is a genuine 

 soiiiile. 



