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



the typical individuals was not wider than one cellular wall 

 of the sperm-duct of the individual now under consideration. 



This fact alone does not render impossible the view that the 

 difference shown in the individuals is really due to distention ; 

 for if the sperm-duct lumen is intercellular, it would mean 

 simply a pushing out of the cells by their inclosed contents, 

 and no necessary alteration in the epithelium itself. The 

 case obviously becomes different, however, if the sperm-duct 

 has an intracellular lumen. In the present specimen there 

 would seem to be every probability that for some distance 

 after the funnel the lumen is intercellular, since the nuclei in 

 the walls of the ducts are fairly closely arranged in the walls 

 of the tube side by side. But later on this is not the case, 

 and I have observed transverse sections of a piece of tube 

 with but one nucleus therein, and pieces of longitudinal 

 section with very few nuclei. This means at least fewer and 

 larger ceils to the wall, if it does not prove an intracellular 

 duct. 



In this region it is to be noted that there is no perceptible 

 dilation of the tube, which is therefore really larger than in 

 the specimen described above. 



I may take this opportunity of observing that the distinction 

 between an intracellular and an intercellular duct is not 

 perhaps of great importance ; but it is, after all, an anatomical 

 difference between the nephridia of the Oligocha^ta and the 

 sperm-ducts of the great majority of those worms. It is thus 

 worth pointing out in the present instance as a character of 

 the genus Trichodrilus, for the observations which I have 

 made upon the example which I now refer to are confirmed 

 by a re-examination of the other specimens of the genus 

 dealt with in the present paper. Undoubtedly intracellular 

 sperm-ducts only occur among the '^ Limicoline" Oligochpeta, 

 and are not commonly met with. Benham"^ has given ample 

 reasons for thinking that the sperm-ducts in his Phreoryctes 

 heterogyne are of such a character. More to the immediate 

 point are Mrazek's figures of Lumbriculus "j" where the atrial 



* " On a new Species of the Genus Haplotaxis, with some Remarks on 

 the Genital Ducts in the Oligochaeta," Quart. Journ. Micr. Sci. (n. s.) 

 xlviii. 1904, p. 304. 



t Zool. Jahrb. t. c. p. 435, figs. J 1, J 2. See especially the latter 

 figure for the atrial part of the sperm-duct. In Tubifex, according to 

 Miss Dixon {loc. cit. pi. iv. figs. 18 A, 19 A, B), the sperm-duct also seems 

 to become intracellular, liut Gateuby (Quart. J. Micr. Sci. (n. s.) ixi. 

 p. 320 &c.) describes and figures the duct (pi. xxiv. fig. 17 E) as inter- 

 cellular. 



