DR. T. S. COBBOLD, FURTHER OBSERVATIONS ON ENTOZOA. 351 



obliquely in reference to the central line, the angle of divergence being about 25°. During 

 the eversion and 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 de- 

 pressions are obviously inversions of the ventral integument, forming socket-like pouches 

 for the implantation 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 hook («, 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 loAver 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 tbe tube at the lower end. Acting 

 antagonistically 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 is flattened 

 out, so as to form a three-cornered process (e), which covers and protects the sharp ex- 

 tremity 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 figure (3), that the uppermost row is placed somewhat 

 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 connexion with them. 



With respect to the internal structure of this parasite, very little can 1)e made out — a 

 cu'cumstance materially favouring the notion that we have to deal with an imperfectly 

 developed animal. Throughout the body there exists a central clear space, and this is 

 well defined by dark lateral masses, which narrow out on either side of the head, in the 

 form of a horse-shoe-shaped band enclosing the mouth and the four chitinous claw-masses. 

 These dark patches at first sight look like albumenogeue organs, but a closer examina- 

 tion shows that they are entirely made up of large parenchymatous cellules, unconnected 

 by any special fibres or tubes. In an isolated and highly magnified group of them, 

 the granular contents and central nuclei at once became visible, as represented in fig. 6, 

 where some have become flattened at the sides from accidental pressure *. 



Before finally quitting the consideration of this parasite, I may advert to the recently 

 advanced opinion of Gurlt, Kllchenmeister and others, respecting its assumed larval con- 

 dition. After the perusal of Leuckart's original memoir t, kindly placed in my hands by 

 Mr. Busk, I naturally felt desirous of repeating that distinguished zoologist's experiments. 

 Accordingly (as I have already stated in the Quart. Journ. Micr. Sc), on the 11th of Fe- 

 bruary, I proceeded to infest two dogs. Into the nostrils of the first hound, stated to be 



* Leuckart, in his recent work, ' Bau unci Entwickelungsgescliiclite tier Peutastonien,' says they are glandular, and 

 finds ducts in connexion with them. 



t Heule and Pfeiffer's Zeitsch. he. aY.— See also my translation in the ' Micr. Journal,' vol. vii. p. 182. 



