90 Mr. F. E. Beddard on the 



definitely shown that in Ilyodrilus, which presents many 

 intermediate characters between Naids and Tubificidse, there 

 is no asexual reproduction, this division seems reasonable*. 



The Lumbricomorpha are " divided roughly " into two 

 Orders, Microdriii or " Waterworms," and Megadrili or 

 " Earthworms." One constant difference alone is allowed to 

 distinguish the two Orders, i. e. the presence or absence of a 

 capillary network upon the nephridia. 



As a matter of fact these groups might be further dis- 

 tinguished as follows : — 



Mio'odrili. Mec/adrili. 



(1) Sexual maturity at a fixed (1) Sexual maturity more or less 

 period. continuous. 



(2) Clitellum consisting of a single (2) Clitellum consisting of two 

 layer of modified cells only. distinct layers of ceUs. 



[S) Ova of large size and few. (3) Ova small and numerous. 



This separation between Microdriii and Megadrili is, how- 

 ever, rendered almost impossible by the structural characters 

 of Ocnerodrilus^ which I have recently had the opportunity 

 of examining. Eisen's account of the anatomy of this form 

 (" On the Anatomy of Ocnerodrilus^'' Nova Acta Reg. Soc. 

 Upsala, 1878), at present the only one, does not agree in 

 every particular with ray own observations. I find that the 

 testes are in the 10th and 11th segments, and the ovary in 

 the 13th ; the sperm- sacs, which do not enclose the testes or 

 vasa deferentia funnels, are in segments 10-13 ; the oviducts 

 open into the 14th segment ; the vasa deferentia open into 

 the 17th segment in company with a glandular atrium. The 

 clitellum extends from the 13th to the 19th segment and has 

 the same structure as that of Lumbricus. 



So far the characters of Ocnerodrilus are those of the 

 Megadrili, but it agrees with the Microdriii in two important 

 points, one of which has been shown by Eisen in a figure, 

 though not commented upon. This character is the total 

 absence of any vascular plexus round the nephridia ; I may 

 further remark that the nephridia of the posterior segments 

 (from the 20th) differ from those of the anterior segments in 

 being surrounded by a mass of large clear cells as in 

 many Microdriii and in Pontodrilus (Perrier, " Organisation 

 des Pontodrilus j^'' Arch. Zool. Exp. t. ix. 1881). In the 

 genital segments of a specimen with fully- developed clitellum, 

 testes, sperm-sacs, &c., the nephridia were present with the 

 exception of the 11th and 12th segments (and here they were 



* It is practically that of d'Udekem (" M<5moire sur les Lombriciens," 

 Premiere Partie. Mem. Acad. Eoy. Belg. t. xxxvi.). 



