230 42 



large; penis short with a muscle sheath and prostata glands. Above the testis a hyaline ovoid 

 mass regarded as rudiment of the alimentary canal; further some gloliules regarded as remains 

 of yolk. Length of female 600— 7ÛÛ,u, male "plus petit". Time: May, July. 



Description. The form of the male differs rather from that of the female; 

 there is no neck, no inflated posterior part and hardly any tail. It has an ellipzoidic 

 form, faintly tapering in the posterior part; it ends in two well developed toes, be- 

 tween which a little protuberance is observed in the female. I have never found any 

 gelatinous sheath, so characteristic of the female. The wheel-organ consists of a verti- 

 cally placed convex disc with a row of short cilia. The auricles are well developed, 

 but very often withdrawn; they are unfolded in swimming, but commonly withdrawn 

 in creeping. On the disc a broad band of long cilia. I have never seen anj' rudiment 

 of a lip, which is extremely well developed in the female. The brain is broad, car- 

 rying a red eye. The dorsal antenna has not been observed ; it is mentioned in 

 Weber's text, but not found in his figure. The two lateral organs, provided with long, 

 sensitive hairs, are very conspicuous. The retrocerebral organ is a large broad pouch, 

 containing rounded or pentagonal vacuoles; at the sides are two small lateral lobes. 

 No openings for the organ have been observed. No sure rudiment of the alimentär}' 

 canal, but between the retrocerebral organ and the testis lies a peculiar large, rather 

 hyaline globule also mentioned by Weber; that this, as supposed by Weber, is a 

 remnant of the alimentary canal, is possible. The excretory organ consists of two 

 long curled canals, provided with four vibratile tags; there is no contractile vesicle; 

 openings for the canals have not been observed. There are two prostata glands near 

 the beginning of the ductus seminalis and two smaller ones more posteriorly. The 

 testis is large, almost globular. As far as I have been able to see, the ductus semi- 

 nalis which is twisted debouches into a very distended much broader part wholly 

 covered on its interior part with cilia. This part opens on the posterior border of 

 the last segment. If and how it is used as penis, I do not know. Weber's drawing 

 indicates the same distension but also that, in his opinion, it has nothing to do with 

 the genital opening. In his drawing the penis opens above this distension which is 

 quite independent of the genital organ. In his description the organ is not mentioned. 

 There are two normal foot glands. There are eight transversal muscle bands, five pairs 

 of longitudinal muscle bands for the wheel-organ and two for the foot. These bands 

 overlap in the middle line of the body. Length of female 6 — 700,«, that of male 

 ca. 300,«. 



In a little peat bog divided into a great many smaller pits at Strodam about 

 three kiJom. from Hillerod I found, in May, in the algæ coverings of the surface in 

 one of the pits, C. lahiafus. in the other, C. pachyurus; especially C. pachyurus was 

 very common; for years the two pits have had no connection with each other. Having 

 isolated about a hundred specimens of both species, some days later a few males 

 appeared. In samples taken in directly from nature, I never saw any males. The 

 colonies were observed in May, but as heavy downpours began in June, the ani- 

 mals became rarer and rarer and finally totally disappeared. 



