184 MR. R. I. POCOCK ON THE [June 17, 



apophysis, which rises from the distal extvemity of the anterioi- 

 bar of the entostemite (text-fig. 44, t'-t"^\ p. 183). The form and 

 position of these diverticula, however, seem to vary considerably in 

 accordance with the degree of their distention with food-particles. 

 When filled from base to extremity they are of faiily uniform 

 width thi'oughout. When partially emjjty their distal portions 

 take the form of slender subcylindrical tubes diftering considerably, 

 both in appeai-ance and shape, fi-om the charged basal portions. 



To this difference is to be ascribed Blanchard's ^ erroneous 

 description of the stomach as consisting of -fou.!- pairs of lateral 

 cpeca, enveloped above and below by a lai-ge tubular or salivaiy 

 gland. In the specimens he dissected, belonging to the species 

 now known as Mastigoproctus antillensis, the four posterior pairs 

 of caeca appear to have been partially emptj^, while the anterior 

 cfeca and the centi'al poition of the midgut were distended. I have 

 found a similar state of things in the examples of Mastiyoprocius 

 giganteus and of Uroprocius assamensis that I have examined, 

 whereas in all the examples of Hyjjoctonusformosus, all collected at 

 the same time, the diverticula were evenly filled thioughout. Hence 

 the possibility that the width of the tei-minal jDortions of the divei-- 

 ticula may vary with the species, and may not be attributable to 

 the cause I have suggested, must be borne in mind. Blanchard 

 neither figures noi' describes the anterior median diveiticulum, 

 present in all the specimens of Thelyphonida? I have examined. 

 Possibly it was not distended in his examples. Apart from this 

 disci'epancy, and from a too sharply defined line of demai-cation 

 between the filled and unfilled portions of the ca-cal diverticula, 

 evidently introduced to emphasize the distinctness of the so-called 

 "tubular" or "salivary" gland, his figux'es admirably repiesent 

 the "stomach" in this group, even to the spaces through which 

 the two pairs of muscles pass to the middle line of the carapace. 

 They also show the two inferioi' median divei'ticula which dip 

 down through the median foramina of the entostemite and 

 extend along its underside. Being filled with food, these were 

 described as part of the tubular or salivary gland. Laurie mentions 

 them as well. This author's description of the thoracic poition 

 of the midgut as expanded into wide latei'al diverticula, which 

 extend ovei' the brain in front and the coxal glands at the sides, 

 each diverticulum being divided into five lobes, is correct so far 

 as it goes, but too insufficiently detailed to criticise. The figure 



1. Blanchavd (Org. du Efegne Anim., Arachnides) described the "stomach" of 

 Thelyplwnus as consisting of a sac giving oflF four pairs of csecal diverticula and 

 enveloped above and below by voluminous glands of two kinds, described in the text 

 as "utricular" and "tubular" glands. The former (=coxal gland), embracing the 

 stomach laterally, are compared to the " salivary " glands, so-called by Newport 

 and Miiller, of the Scorpions. 



How Blancliard and others, for reasons that need no explanation, ascribed an 

 alimentary function to the coxal gland is now ancient history ; but his mistake in 

 homologizingthecoxalglandsofT/(e?_?/p7iowMs with the prosomatic midgut diverticula 

 of Swfhus is less intelligible. A further error into which he fell was the inter- 

 pretation of part of the midgut diverticula in Thelyplwnus as a "tubular " digestive 

 gland. 



