Dr. F. E. Beddard on the Oenus Trichodrilus. 233 



Whether they extend further than this I do not know. They 

 contained large ripe ova with the usual abundant yolk. 



The sperm-ducts are in segments IX. , X., XI., and open on 

 each side by the atrium on to the tenth segment. The 

 funnels are in the ninth segment and the tenth, and are much 

 as figured and described by Claparede in this, and, by him 

 and others, in other Lumbriculids allied to Trichodrilus. The 

 funnels were, as is usual, conspicuous owing to the bundle of 

 spermatozoa caught up by the ciliated mouth of each. The 

 main part of the posterior pair of sperm-ducts forms a coil in 

 the eleventh segment close to the anterior wall of that segment. 

 I did not observe the actual openings of the sperm-ducts into 

 the atrium with absolute certainty. The funnels, instead of 

 being flattened over the septum and plate-shaped, are cup- 

 shaped, as Hesse (quoted below) figures in Lumbriculus *. 



The atrium is generally as recorded by Claparede f. It is 

 noteworthy for the very thick circular muscle-layer figured by 

 that author, and subsequently by Ditlevsen \ and Piguet §. 

 Its duct to the exterior is narrow and projects as a penis into 

 an ingrowth of the epidermis, forming a small circular cavity. 

 This is not indicated by Claparede. As I point out later, the 

 characters of the atrium may distinguish this genus from 

 Phreatothrix. Hesse ||, and, later, Mrazek^[ have given 

 figures of the atrium of Lumbriculus, and the first-named has 

 compared it with that of Claparedilla, Rhynchehnis, Stylo- 

 drilus, and Trichodrilus, remarking that these forms have 

 always glandular cells outside of the atrium, but never 

 muscle-layers as in Lumbriculus. This in spite of Claparede's 

 figure referred to by him. However, Hesse appears to be 

 correct in his statements of the other genera mentioned in 

 his list, admittedly taken from the writings of others **. It 



* Or perhaps they would be better described as funnel-shaped. Miss 

 Dixon (Tubifex, Liv. Mar. Biol. Comm. Memoirs, xxiii., London, 1915) 

 remarks (p. 58, cf. pi. iv. figs. 17, 18) that the funnels of Tubifex are 

 cup-shaped in the more immature worm, and more expanded later. 



t Mem. Soc. Phys. Geneve, t. c, pi. iii. fig. 6. Claparede does not 

 indicate the lining epithelium of the atrium. 



J " Studien an Oligochaten," Zeitschr. wiss. Zool. Bd. lxxvii. 1904, 

 p. 441, Taf. xvii. fig. 49. 



§ Rev. Zool. Suisse, t. c. woodcut, p. 141. 



|| " Die Geschlechtsorgane von Lumbriculus variegatus, Grube," 

 Zeitschr. wiss. Zool. Bd. lviii. 1894, p. 355 (also published as Bd. i. no. 1 

 of ' Tiibinger Zoologische Arbeiten "). 



il "Die Geschlechtsverhaltni3se und die Geschlechtsorgane von Lum- 

 briculus variegatus, Gr.," Zool. Jahrb. Bd. xxxiii. 1906, p. 381. 



** More lately Michaelsen has figured (Bull. Ac. St. Petersb., Sept. 1901, 

 pi. xi. fig. 19) a circular muscle-layer in Rhynchehnis bracliycephala. 



