73' 261 



Curiously enough it seems that tlie male has only been found a few times 

 after it has been observed by Brightwell and Dalrymlpe; it is figured by Hud- 

 soN-GossE 1889, PI. XII, PI, 1 c, but no new observations are added to the old ones. 



Asplanchna Sieboldi Leydig. 



Male: Leydig (1855, p. 30). 



Hudson-Gosse (1889, p. 121). 

 Daday (1891, p. 87). 

 Tab. VII, fig. 3. 



Leydig (1855, p. 30, Tab. II, fig. 12 — 14) has given an excellent description 

 and very good drawings of the male. 



The form differs from that of the female, not being campanulate but cone-shaped, 

 with two pairs of humps, one pair larger; almost in the middle of the body, and one pair 

 nearer to the corona; during the swimming motion the arms are stretched out and drawn 

 in. The wheel-organ is in full accordance with that of the female, the coronal disc carrying 

 the same elevations with stiff setae and bunches of bristles as this sex; the brain gives off 

 nerves to the elevations with the setæ on the disc and to the ventral lateral antennæ; the 

 dorsal pair is not mentioned. No alimentary canal; the excretory organ in full accordance 

 with that of the female (vibratile tags about 50). The large testis pear-shaped; ductus semi- 

 nalis in its interior covered with cilia and provided with prostata glands; the structure of 

 the spermatozoa is thoroughly described. Muscular system in accordance with that of the 

 female, strong longitudinal muscles and fine transversal bands, of which one pair are used 

 to draw in the humps; on the base of the humps they appear "sternförmig", sending off fine 

 threads to the periphery. In the bod^' cavity behind the great humps cell material which 

 Leydig regards as stored nutriment deriving from embryo. Leydig's drawings were subse- 

 quently reproduced by Toth (1861, p. 178, Tab. II, fig. 13—14). 



HuDSON-GossE (1889, p. 121, PI. XI, fig. 3) have given a very good description 

 and drawing of the male as Asplanchna ebbesborni. 



It must especially be pointed out that H.-G. have observed the rounded masses adhering 

 to the dorsal surface, just below the humps. They are in accordance with Leydig but with 

 some doubt, regarded as "a kind of stored-up material to compensate for the male's inability to 

 take nourishment«. The muscle system of the penis and testis is well described and so also 

 especially the excretory system with the flocculent ribbons, the tubes and the large number 

 of vibratile tags (about forty on either side). 



Daday (1891, p. 87) gives a very insufficient drawing of the female and de- 

 scribes it shortly as follows: 



"Körper vorn cylindrish, mit zwei bauchständigen Anhängen, hinten conish, mit zwei 

 kräftigen Seitenanhängen; — mit einem einzigen Stirnauge." Size 200—400 ft, female 800— 1500 /<. 



Description. Form of the body not bellshaped as in the female, but conical 

 as indicated by Leydig. It is provided with two sleeve-like prolongations, situated 

 almost in the middle of the body; of the two others placed nearer the wheel-organ 

 and indicated by Leydig and Hudson-Gosse I have only seen slight vestiges. The 

 prolongations may be drawn in and out during the swimming motion; they are 

 always empty; the whole animal extremely hyaline. 



U. K. U. Vldensk. Selsk. Skr., nalurv. og matheni. Afd.. 8. Række, IV, 3. 35 



