398 



ENTOZOA. 



retractation of the claws, the vacant spaces directly above them 

 dilate and contract, so as greatly to facilitate the prehensile action 

 of the hooks. These depressions are obviously inversions of the 

 ventral integument, forming socket-like pouches for the implanta- 

 tion of the hook-capsules. If one of the claws be isolated and 

 viewed laterally, it will be seen to consist of two parts — namely, 

 a strongly-curved hooh {a, fig. 4), and a capsule (b). The upper 

 part of the latter forms a hood (d), for the lodgement, support, 

 and protection of the hook ; the lower tubular portion serving to 

 fix the apparatus in the body, and at the same time to regulate the 

 movements of the claw through the intervention of a muscular 

 pulley (g), which enters the tube at the lower end. Acting antago- 

 nistically to this, we find an extensor muscle (/) inserted into the 

 anterior border of the base of the hook itself. The summit or 

 projecting point of the hood (Spitzendecher of Kiichenmeister) is 

 flattened out, so as to form a three-cornered process (e), which 

 covers and protects the sharp extremity of the hook when the 

 latter is retracted. 



In regard to other external appearances, my observations, for 

 the most part, correspond with those already on record ; but with 

 reference to the rows of minute integumentary spines, it will be 

 seen from my drawing, that the uppermost row is placed some- 

 what more apart from the second — at least, at the sides ; the whole 

 forming a complete and graceful tracing, as it passes downwards 

 on either side between the inferior and superior pair of cephalic 

 claws. Further, I do not find the spines themselves to be simply 

 conical, as hitherto represented, because their uniformity of outline 

 is interrupted at the lower third (as shown at the left margin of 

 figure 5) ; this appearance, indeed, can only be seen by a lateral 

 view. The so-called stigmata {Athemlocher of Nordmann) display 

 a double outline, but no vessels could be traced in connection with 

 them. 



With respect to the internal structure of this parasite very 

 little can be made out, a circumstance which in itself favours the 



