182 MR. R. I. pococK ON THE [June 17, 



The pharyngeal portion of the foregut in TliehjiDlionus which 

 opens at its anterior end into the slit above described is a wide 

 membranous tube, strengthened with four chitinous strands, a 

 right and left upper and a right and left lower. The latter are 

 directly continuous with the chitinous plate forming the iioor of 

 the suboral trough ; the former with the posterior extremity of 

 the lower surface of the camarostome forming the roof of the 

 trough. From its doi'sal walls muscles pass to the undei' surface 

 of the median entosclerite which arises from the membrane above 

 the base of the camarostome, and from its sides muscles extend to 

 an injutting process from the coxa of the chela ^ (text-fig. 41, 

 A, B, ent.^ c«.p., p. 173). 



It thus constitutes a powerful, dorso-ventrally compressed, 

 jDharyngeal or pre-cerebi'al sucking apparatus, homologous to that 

 of the Scorpions and Spidei's (text-fig. 43, D, ])h.^ p. 180). In the 

 Scorpions, however, the organ is compressed fi'om side to side, 

 and its lateral muscles pass to the crescentic preoi'al entosclerite, 

 which represents the median entosclerite above the camarostome 

 of Thelyjyhonus^ (text-fig. 43, A, B, ent., ph., p. 180). 



From this point the foregut narrows and runs backwai'ds 

 through the brain as a i-elatively soft, flexible, and weakly 

 chitinous tube. Between the brain and the anterior biidge of 

 the entosternite it forms a lanceolate expansion, compaiuble 

 to the so-called " sucking-stomach " of the SjDiders, though not, 

 apparently, supplied with the powerful dilatoi- and conti-actor 

 muscles characteristic of this organ in the last-named order. 



Behind this expansion the gut passes between the descending 

 branches of the aorta and expands into the saccular stomach of 

 the midgut. This is provided with five pairs of principal diverti- 

 cula, which are often of ii-regular shape and sometimes asym- 

 metrically branched, and extend towai-ds the coxae of the postoral 

 appendages, sometimes dipping into the cavities of those of the 

 legs (text-fig. 44, 1-5, p. 183). The diverticula of the anterior 

 pair arise behind the descending portion of the aorta, and passing 

 forwards on each side of it, unite in the middle line, thus circum- 

 scribing a space through which, in addition to the aorta, the 

 obliquely ascending pair of apophyses from the entosternite runs 



1 From Laurie's description it is not clear which of the two apertures, i. e. that at 

 the distal or at the proximal end of the camarostome, he signifies hy the word 

 " mouth." Probably scarcity of material prevented an accurate dissection of this 

 region ; otherwise it is difficult to account for the misleading statement that the 

 foregut (stomodseum) of Thelyplio'tms has "no appearance of a dilatation into a 

 sucking stomach such as is found in the Scorpion "; nor for the erroneous assertion 

 that " the muscles of the anterior part of this stomodseum" pass to three chitinous 

 processes running back from the camarostome. Two of these three entosclerites are 

 the injutting angular processes of the coxae of the chelae, and the third arises from 

 the membrane above the camarostome. 



" It is singular that Blanchard (Org. du Eegne Anim., Arachnides) overlooked 

 this enlarged pre-cerebral pharyngeal sucking portion of the alimentary canal in 

 Thelyphonus. The same oversight characterizes his observation upon this region in 

 ' Mygale,' and, as Huxley pointed out, in Scorpio. In tlie case of Fhrynus, 

 however, he both figured and described it, homologizing it with the oesophageal 

 portion of the canal in Tlielyplionus. 



