196 



ENTOZOA. 



lengtli of these horny filaments to be i^", whilst their breadth is 

 3570". On the whole we may regard this organ as a complicated 

 form of " holdfast " designed to faciHtate or giye efficiency to the 

 sexual act. I may here also state that this structure is by no 

 means unique, for, if I mistake not, it exists in an equally 

 developed degree in the young trematode which Dr. Leared found 

 infesting the heart of a turtle. Leared believed that he had 

 found a true distome, an opinion to which I could not give my 

 assent, seeing that the organ described by him as a " folded, 

 ventral sucker," presented a very different aspect to the genuine 

 oral sucker displayed by the same animal. I am now persuaded 

 that the structure in question, which is, to a certain extent, 

 characteristic of his so-called Distoma constrictum, is analogous to 

 the supplementary "holdfast" existing in Distoma heterophyes. 

 The opinion also which I then advanced as to the probable source 

 and condition of the parasite, I still see no reason to retract.* 



In regard to the anatomy of D. heterophyes, I have only 

 further to observe that a special set of glandular organs is 

 situated on either side of the elongated oesophagus, but the con- 

 nection between these striictures and the digestive apparatus is not 

 clearly made out. Leuckart compares them to the so-called salivary 

 glands found in Distoma lanceolatum, and says, " The presence 

 of such a glandular apparatus is also indicated by the more 

 ventral position of the oral sucker, and the development of the 

 cephaKc margin." The conspicuous contractile vesicle terminatiag 

 the excretory system is developed to an unusually large extent, 

 exhibiting in its interior multitudes of the well-known active 

 molecular particles. The ova present a rich reddish-brown colour, 

 having a rather broadly oval figure, and measuring ^^ of an inch 

 in length, by j^" transversely. 



* Dr. Leared's brief description of this parasite is given in the lOth vol. of the 

 " Quarterly Journal of Microscopic Science," p. 169, and is accompanied by an accurate 

 woodcut. New Series, Vol. II. for 1862. He also found in the blood a quantity of ova 

 precisely like those which Mr. Canton had previously described as adhering to the 

 conjunctivse of turtles' eyes. See a paper in the same Journal for 1861, Vol. I. N. S., p. 40. 



