86 Records of the Indian Mxiseani. [Vol. XY, 



IV. Systematic position of the worm. 



It will be clear from the preceding description that the parasite 

 presents many unique characters. Our first impressions were that 

 the parasite was a Trematode, but subsequent investigation showed 

 that this was not the case. The entire absence of an alimentary canal, 

 and the presence and arrangement of the four suckers, suggested the 

 probability of the parasite being a Cestode, and it was only after care- 

 ful examination that we concluded, definitely, that the animal belonged 

 to the Cestoda. 



Benham (1) defines the characters of the Cestoidea and the Trematoda 

 as follows : — 



(1) Cestoidea. — ^Platyhelminths in which an internal parasitic habit 

 has led to the disappearance of the alimentary canal from every stage in the 

 life-history.^ The ciliated covering, as well as definite organs of sense, 

 are likewise absent in the adult. The epidermis, which has sunk into 

 the parenchyma, secretes a thick cuticle as in the Trematoda. In the 

 parenchyma, certain lime-secreting cells are developed in greater or less 

 number. Organs of fixation are developed in a characteristic, but 

 varied form, at one extremity of the worm. 



(2) Trematoda. — Parasitic Platyhelmia which retain the mouth and 

 alimentary tract of the ancestor, but in which the epidermis not only 

 loses its cilia during embryogeny but is apparently absent in the adult 

 as a distinct continuous cellular layer, having sunk into the mesoblastic 

 tissue after secreting a thick, stratified, chitinous cuticle. Further, in 

 relation to their parasitic habits, suckers are developed at, or near, the 

 posterior end on the ventral surface and also in the region of the mouth. 



In considering the classification of the worm just described, three 

 points are to be considered, viz. : — 



(1) Is the animal a Trematode or a Cestode ? 



(2) Is it a larval form or an adult ? 



(3) If an adult, then is it a primitive or a degenerate form ? 



(1) Is the animal a Trematode or a Cestode ? 



The entire absence of all traces of an alimentary tract, the disposi- 

 tion of the suckers, and the absence of ventral posterior suckers are 

 definite Cestode characters which, in our opinion, show that the worm 

 is not a Trematode. The absence of an alimentary canal alone is con- 

 sidered by Luhe, and other leading helminthologists, to be the chief 

 distinguishing character between Cestodes and Trematodes, although 

 in some stages of the life-history of a few Trematodes, owing to 

 degeneration, all traces of an alimentary canal disappear. We were 

 unable to establish, by experiment, the actual presence of calcareous 

 bodies, although under the microscope, typical calcareous bodies appeared 

 to be present. The occurrence of orange-red corpuscles is an incidental 

 character which it shares in common with many adult Tetrarhynchids, 

 but we are not aware of any record of such coloured bodies being 

 found in the Trematodes. Although the parasite seems to us to be 

 undoubtedly a Cestode, we are aware that it differs very widely from 



^ The italics are ours. 



