TEE MA TOD A 



35 



FIG. 4. The small Egyptian 

 fluke (Distoma heterophyes), 

 viewed from behind. The 

 large ventral sucker, supple- 

 nieutary disk, uterus, testes, 

 simple divided intestine, 

 vitellarium, and pulsatile 

 vesicle are conspicuous. 

 Original. 



basket-like horny ribs comparable to the claw-formations seen 

 in the genus Octobothrium. According to Bilharz these ribs 

 give off five little branches from their sides, 

 but Leuckart could not see them in his 

 specimens. Leuckart estimated the length 

 of these horny filaments to be y^", whilst 

 their breadth was ' '. On the whole we 

 may regard this organ as a complicated 

 form of " holdfast " designed to facilitate 

 or give 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 an ordi- 

 nary 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 oral sucker displayed by the same 

 animal. Without doubt, however, the organ in his so-called 

 Distoma constrictum is analogous to the supplementary " hold- 

 fast " existing in Distoma, heterophyes. The views which I 

 originally advanced as to the source and condition of the parasite 

 are probably correct. 



As regards the structure of Distoma heterophyes, I have only 

 to add that a special set of glandular organs is situated on 

 either side of the elongated oesophagus, but the connection 

 between these organs and the digestive apparatus has not been 

 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 cephalic margin." The conspicuous contractile vesicle 

 terminating the excretory system is developed to an unusually 

 large extent, exhibiting in its interior multitudes of the well- 

 known active molecular particles. Lastly, I have only to add 

 that the eggs of Distoma heterophyes measure ~ f in length by 

 -535" transversely. 



BIBLIOGRAPHY (No. 8). Bilharz, (< Beitrag zur Helminth, 

 humana," ' Zeitsch. fiir wissenschaftl. Zool./ s. 62, 1851. 



