MONOSTOMUM LENTIS. 245 



sucker is therefore deficient, and Diesing gives a warning, 

 " Cave, ne Bothriocephalidearum articulum solitarium pro ' Mono- 

 stomum' habeas, aut porum genitalem, interdum callosum, cum 

 acetabulo confundas." 



1. ? Monostomwn lentis (Von Nordmann). 



In the month of May, Professor Jiingken extracted a lens 

 which was not quite obscured and was still soft in its substance 

 (incipient cataract), in the upper strata of which there were eight 

 Monostoma. They were -L'" in length and moved, although but 

 slowly, when they had lain in warm water. 



This is all that we know of this trematode worm, and all my 

 endeavours to get sight of a specimen have been fruitless. 

 Professor Jiingken writes me that he handed over the animals 

 to Von Nordmann, and that he unfortunately does not know 

 what has become of the preparation. All my further in- 

 quiries also as to what has become of Nordmann's preparations 

 have hitherto been unavailing. I can therefore only give a 

 general opinion upon the case, and at least, as it appears to me, it 

 is very possible that Von Ammon's Distoma and the Monostoma 

 lentis of Nordmann are identical, that is if a trematode worm is 

 really in question here. If, on the one hand, Diesing warns us 

 against taking the porus genii alls of separate segments of 

 Bothriocephali, which is sometimes callous, for a sucking cup, and 

 thus making Monostoma out of structures which are nothing of 

 the kind, the following words of Dujardin also show that even 

 distinguished observers (amongst whom Von Nordmann is un- 

 doubtedly to be placed) have deceived themselves, and declared 

 things to be Monostoma, which were rather Distoma. Thus 

 Dujardin, speaking of the Monostomum ocreatum of the mole in 

 his ' Hist. nat. des Helminthes/ p. 344, where he describes this 

 as identical with Distoma lorum, says, " de mon cote, en cher chant 

 ce Monostome a Rennes, fai trouve non un Monostome, mais un 

 vrai Distome filtforme, que fai reconnu etre le meme helminthe, 

 en comparant trois exemplaires envoyes de Vienne au Museum de 

 Paris." 



It is only from the want of opportunity of examining for 

 myself that I have still allotted Nordmann's entozoon a separate 

 place here. Diesing also appears to think that the Monostomum 

 discovered by Nordmann is identical with Von Ammon's 



