1895.] HTDEACHNID FOUND IN COENWALL. 181 



widest part, of about '03 mm. ; when, however, we come to the 

 construction of the pharynx, and indeed to the question of what 

 really is the pharynx, I do not find that my species at all agrees 

 with Schaub's description and drawings. Of course, as I have not 

 seen Schaub's species, I cannot in any way deny that he is correct 

 as to that species ; but if he be, then it seems to me that his species 

 must be quite exceptional, differing entirely not only from what I 

 believe I see in Thyas &c., but also from what Croueberg has 

 described in Eijlais, and Henkin iu Tronthidium. The appearance is 

 so similar in all these cases that the investigator is tempted to doubt 

 whether the difference may not be one of interpretation rather than 

 of actual cousti-uction ; it is, however, not merely a difference of 

 small detail but of principle. It we refer to Schaub's Taf. i. fig. 1, 

 we shall find that he draws the pharynx (p^.)as a fusiform sac con- 

 tinuous in a straight line with the oesophagus, and lying above and 

 upon what he calls a chitinous floor (" Chitin Boden '') (his ch. 2), 

 into the top of which floor the long, almost perpendicular, muscles 

 coming from above are inserted ; this floor he makes joined at its 

 end to a lower chitinous floor (c/t. 1), which forms the true floor of 

 the mouth ; so that the two together form a V with the point 

 directed back\A ard and not allowing any food to pass between the 

 two limbs of the V, or at all events not to pass beyond the point 

 of union of these two limbs. If we now turn to Schaub's Taf. iii. 

 fig. 6, which is a horizontal section through what he considers to 

 be the pharynx, we find that he considers that organ to be divided 

 into numerous compartments by what he calls disks (" scheibenfor- 

 mige Querflachen "), each compartment containing a ring-muscle 

 which constricts an extremely fine tube passing longitudinally up 

 the middle of the pharynx ; this tube he says is the true tbroat 

 (" Schlundrohr "). through which the food passes. There is not 

 anything to show how this throat expands again when the ring- 

 muscles are relaxed; it would seem to be probably too delicate 

 to do so from its proper elasticity. If we now refer to Henkin's 

 figs, o and 7, we shall find that (in Tromhidium) he draws most of the 

 similar parts, but puts a totally different interpretation upon them. 

 Schaub's upper chitinous floor (his cli. 2), to which the muscles are 

 attached, is Henkin's " upper wall of the throat " ; Schaub's lower 

 chitinous floor(c7j. 1) is Henkin's "under wall of the throat"; Schaub's 

 disks are represented (in Henkin's fig. 7) by the tendons which 

 attach the long perpendicular muscles (Henkin's " sucking muscles") 

 to the upper wall of the throat ; the upper and under walls, when 

 at rest, still form the V shown by Schaub, but they are not joined 

 at the point, and when the sucking-muscles contract the upper 

 wall of the throat is raised, a sucking action is the result, and the 

 food rushes in between the two walls. The fine tube which Schaub 

 calls the throat has not any existence iu Henkin's descriptions or 

 figures, nor are any ring-muscles to be found, but the latter are 

 represented by transverse muscles (called by Henkin " swallowing 

 muscles ") in the following manner: — The upper and under walls of 

 the throat are not flat surfaces ; they are half-tubes like the rain^ 



