316 T. B. ROSSETEE ON CTSTICERCUS OF TJEN1A LIOPHALLUS. 



16 and 17) ; in fact so much are they alike that the casual ob- 

 server could easily be led into the error of a wrong diagnosis of 

 the species. My reason for selecting the hook is, as I have 

 said before, because in the Cysticercoid stage it is the chief 

 object we have for comparison with those of the mature tape- 

 worm so as to define and affiliate the species. The hooks of 

 each of these species are the same in number — ten — and the 

 same measurement in length, viz., 0035 mm. -0*038 mm., and 

 there is but little dissimilarity in their conformation, but to 

 a critical observer these trifling dissimilarities soon make 

 themselves apparent. In the first place the end of the posterior 

 root or shank— this is the portion of the hook which is towards 

 the apex of the rostellum — of Tcenia setigera is drawn out to a 

 finer point and more deeply curved than that of T. liophallus ^ 

 the anterior root, too, is somewhat finely pointed, whereas that 

 of Liophallus is bossed or thickened ; the concavity or incurv- 

 ing of the hook in the region of the anterior root is deeper in 

 Setigera than in that of Liophallus, whereas the whole hook of 

 Liophallus is gracefully curved from point of claw to anterior 

 root, and much stouter in consistency than that of Setigera. 

 In the second place, as I have said above, the hooks of both 

 these species of tape-worm, whether in the perfect scolex or 

 Cysticercoid stage, measure the same, viz., 0*035 mm., and are 

 ten in number. Yet there is even in this respect a factor to be 

 taken into consideration, as will be seen and understood by the 

 following discrepancies in the measurement. For convenience 

 sake we divide the hook into two parts — from tip of hook to 

 anterior root, and from tip of hook to posterior root or 

 shank. The former is written a-b, and the latter ci-c, and 

 reads thus : — 



Hook of C. liophallus... a-b, 0*010 mm. — a-c, 0*035 mm. 

 „ C. setigera ... a-b, 0007 mm.— a-c, 0035 mm. 



0*003 mm. 



Thus the hook of Liophallus is 0*003 mm. longer from a-b, 

 and 0*003 mm. shorter from a-c than that of Setigera. 



These facts serve to enable us to distinguish the hooks of 

 the two species, both in their Tsenia as well as in their 

 Cysticercoid stage, and must be taken into consideration in 

 judging, forming a conclusion, and arriving at a decision as to 



