Dr. L. Orley on Nematodes, 303 



Zoological Department, I received permission to examine 

 the collection, and was assisted in every way by Prof. 

 JetFrey Bell ; I then exerted myself to arrange it according 

 to the most recent system. I confess I found difficulty 

 in deciding on which system to proceed ; for, as is well 

 known, various opinions prevail on the subject. Laying aside 

 the old classifications of Rudolphi and Diesing, there remain the 

 views of Bastian, Dujardin, and JSchneidcr, and, further, those 

 important discoveries which have been made by Leuckart and 

 Glaus on the Rhabditidaj and by Biitschli and de Man on 

 free-living forms. I must say, at the same time, that our 

 knowledge is, relatively, so poor with regard to the two latter 

 groups that a monograph especially of the llhabditida3 is much 

 to be desired. Our acquaintance also with the general deve- 

 lopment of the Nematodes is very limited, so that we have 

 no characters except those of the anatomy and biology by 

 which to direct our systematic arrangement of the group. 



The first question to be solved is whether the free-living 

 should be placed with the parasitic forms, or whether the two 

 should form independent groups. 



]ii answer to this, diflerent investigators have put for- 

 ward ditferent opinions. Dujardin* and Schneider f placed 

 the free-living and parasitic forms together, while li)astian| 

 considers them to be independent of each other. 'J.'he two 

 first named had but little acquaintance with the free-living 

 forms, while the latter investigated both groups profoundly, 

 leaving however, unfortunately, the Ilhabditidib out of con- 

 sideration. 



In the system of Dujardin we find all free-living forms 

 united under the name " Enopliens," with two parasitic 

 genera PassaJurus and Atractis, a proof tluit they had some 

 characters in common. When our knowledge became so 

 immensely increased by the investigations of Bastian we came 

 into the possession of characters which admitted of the sepa- 

 ration of the two parasitic genera. Schneider endeavours to 

 classify both groups by the muscular system ; but Biitschli § 

 and other workers have sufficiently ])roved that by it the most 

 closely related forms are separated. 



Since Leuckartll and Clausal carried out their studies on 



* Hist. uat. d. Helm. (Paris, 18 Jo). 



t Mouograpliie der Ncniatodeii (lierliii, ]8G()). 



f " Moiiognipli of the Aniruillulida'," Transactions of the Liiuieau So- 

 ciety of London, vol. xxv. 16V>'>. 



§ Beitrage zur Kenotniss derfreilebenden Nematoden (Dresden, 1873). 



II Meuschlicbe Parasiteii, IHC;) and 187(). 



^1 Beobachtungeu iiber die Organisation and Forlpllarzung von Lcptu- 

 dera appendiculata (Marburg, 18(JU). 



