Mr. A. Tulk on tlie Anatomy of Plialanglum Opilio. 245 



along its under surface, the sides of this groove projecting into 

 the cavity of the pharynx, as two sharp incurved ridges. The an- 

 terior half of the plate appears also to be provided with a minute 

 channel continuous with the above. Upon either side, and supe- 

 riorly to this plate, the pharynx is raised into two longitudinal 

 and linear ridges, which are continued, almost parallel with each 

 other, as far as the commencement of the oesophagus, and are fur- 

 nished externally with elongated conical projections, which give 

 attachment to the tendons of numerous transversely striated mus- 

 cular fasciculi, some of which pass upwards, others obhquely down- 

 wards upon the side of the pharynx. Upon each side of the pha- 

 rynx is a pair of short horny teeth (PI. IV. fig. 15. ^) lying close 

 to each other, and which project inwards and slightly upwards 

 towards the posterior half of the dorsal plate. Upon their outer 

 sides are similar ridges for the insertion of a horizontal set of mus- 

 cular fibres (m) ; besides which, other muscles extend transversely 

 {w}) over the pharynx, as far as its posterior termination. The 

 pharynx is broadest in the middle, and narrows again towards the 

 commencement of the membranous oesophagus (ce), which, after 

 bending downwards from the above, passes over the thoracic 

 ganglion and forms a slight dilatation [d), previous to expanding 

 again into the large gastric sac (PL IV. fig. 18. G). 



Connected with the above conditions of the pharyngeal tube in 

 Phalangium, it is interesting to find corresponding modifications 

 in the process by which these creatures derive their aliment. The 

 Araneida, from the extreme minuteness of that structure and of the 

 oesophageal canal, are enabled to live only by sucking the juices 

 of the dififerent insects upon which they prey. The harvest-spiders,, 

 carnivorous also in their habits, combine, however, the power of 

 mastication with that of suction, — a double operation, which would 

 appear to be performed in the following manner. It will have 

 been seen, in treating of the maxillary organs, that owing to the 

 continuity of the first pair of jaws with the margins of the epi- 

 stome, and of the second pair with those of the labium, the hori- 

 zontal action of these parts against each other, as in insects, must 

 be, to a certain extent, prevented, and they work accordingly in 

 the reverse or vertical (Erection, the anterior, the most moveable, 

 playing to and fro in the concavity formed by the second pair 

 with the lower lip, and thus crushing the food " by friction," as 

 was observed by Treviranus. In addition to these peculiarities, 

 the horny bow of the first maxillae is united to the anterior part 

 of the pharynx upon either side, so that when the muscles of the 

 latter act they may probably stretch upon it, and thereby render 

 tense the hollow pouches upon which it i;ests. By these, as by a 

 couple of pads, the body of the captured insect may then be com- 

 pressed and crushed, so as to cause the fluids, aided by the capil- 



