OCR Text |
Show 86 ANNELID OBTAINED DURING THE " SKEAT EXPEDITION." [Feb. 5, it is of larger calibre, and the cells are not so thoroughly stained by the carmine ; it is, in fact, of a more glandular appearance. This section of tube widens a little before it becomes continuous with the first part of the spermiducal gland proper. The latter is quite different again from the terminal part of the spermiducal gland, a fact which appears to distinguish B. iris from B. vejdovskyanum. Iu the latter there is, judging from Stoic's figure, no difference whatever between the proximal and the distal regions of the spermiducal gland. In the species with which I a m here concerned, the proximal section of the glandular tube is of rather limited extent. Its lumen is fairly wide and is lined by tall columnar cells, which are crowded with rounded spherules of secretion. They are not much stained. In Stoic's figure the "parafriuin" is represented as arising from the terminal male tube at about halfway between its commencement and the external orifice. In B.iris the same is the case, and the point of origin nearly represents the passing of the purely glandular part of the spermiducal gland into the distal region, which has quite other characters. The distal part of the tube is wide and has collapsible walls, a fact which is due to their thinness. The epithelium lining the tube here is quite non-glandular. It is a low columnar epithelium which is covered externally by a rather lax covering of muscles. The paratrium has the egg-shaped form which it exhibits in the other species of the genus. There is, however, no cap of divergent *' prostatic " cells such as are figured in B. vejdovskyanum. The paratrium has very thick muscular walls, and its lining of cells becomes deeper and more glandular in appearance at the blind end of the sac. Where the spermiducal glands open on to the exterior of the body they naturally have to burrow beneath the nerve-cord. The latter is raised to near the intestine, and a slip of muscles forming a thick septum connects it with the ventral body-wall after the two spermiducal glands are separated from each other. The ovaries lie in the xiith segment; but I have not discovered the oviducts. The genus Bothrioneuron may be defined and its species discriminated as follows :- Genus BOTHRIONEURON, Stole. Tubificids of 40-50 mm. in length. Setae entirely uncinate. Prostomium with an unpaired, often asymmetrical sense-organ1. Male pore single and median or paired ; atrium with a lateral diverticulum, the paratrium. Sperinathecae absent. Oviducal pores paired '. Spermatophores of peculiar form attached to neighbourhood of male orifice. Hab. Europe ; S. America ; Malay Peninsula. 1 Fide Michaelsen, " Oligochieten" in ' Tierreich,' Berlin, 1890, for statement that the sense-organ characterizes the genus. I a m unable to read Stoic's paper, which is in Bohemian. s In B. vejdovskyanum. They are not known in the other species. |