00 MR. H. CHARLTON BASTIAN'S MONOGRAPH 



tt C(Bca. 

 6. Oncholaimus. 7- Dorylaimus. 8. Odontobius. 9. Diplogaster. 



** Anoplostomata. Os edentatum. 

 10. Dicelis. 11. Anguillula. 12. Angiostomum. 1.3. Leptodera. 14. Isacis. 



Genera inquirenda. 

 15. Phacelura. 16. Potamonema. 17. Nema. 



More extended observation has convinced not only myself, but also Dr. Eberth, that 

 this character, derived from the presence or absence of cirrhi, selected by Diesing as a 

 family distinction, is altogether too inconsistent and variable. Several of the genera 

 placed by Diesing in that family the members of which are supposed by him to have 

 no cirrhi contain species which are abundantly furnished with these appendages, such 

 as Enoplus, Oncholaimus, and Odontobitis ; and, moreover, their presence or alisence is 

 not always a character of sufficient importance to be employed even as a generic dis- 

 tinction. Five of these genera too, Dicelis, Angiostomum, Leptodera, Isacis, and Pha- 

 celura, are composed of species which are not free Nematodes at all, but parasitic forms 

 infesting various kinds of insects, mollusks, myriapods, &c., concerning which I have 

 already expressed my unwillingness to admit their identity with the free Nematoids till 

 such a relation shall be fully established by a more accurate and precise knowledge of 

 their anatomy than we at present possess. 



Dr. Eberth also rejects this arrangement of the free Nematoids by Diesing as imsatis- 

 factory, and offers in its place a readjvistment of his own. He divides them into two 

 principal families, but is doubtful and uncertain about some genera, such as Dorylaimus, 

 Diplogaster, Phanoglene, and Pontonema. His main divisions are as follows : — 



1. Anguillula. 



a. Nematodes with an unarmed mouth, with a cylindrical oesophagus, and well-marked stomach ; 



without tail-glands or ocelli ; partly free and partly parasitic. 



b. Nematodes with an unarmed mouth and simple oesophagus, without stomach and without 



tail-glands. 



2. Urolabes. Nematodes without well-defined stomach, partly with and partly without cirrhi around 



the mouth ; with or without ocelli, but provided with well-defined tail-glands. Habitat, fresh 

 and salt water. 

 «. Apharyngea. 



Amblyura. Phanoglene. Enchelidium. 



b. Pharyngea. 



* Cseca. Oncholaimus. Odontobius. 



** Ocellata. Enoplus, 



This classification is also extremely defective, though leased upon characters having 

 real importance, instead of such mere individual peculiarities as were adopted by Diesing. 

 Eberth has also unfortunately attempted to range all the twenty-three new marine 

 species discovered by himself under five of the old genera, with the result of greatly con- 



