43 2.S1 



Copeus pachyurus Gosse. 



Mille: Dixon Nuthill 1893. 

 Tab. II fig. 2. 



DixoN-NuTTALL (1893 p. 333 Tab. 15) has given a good description and fine draw- 

 ings of the male. 



"In general outline they are very nuieli like thai of a young female, are re.slles.s little 

 fellows, and, unlike the females, seldom withdraw their auricles, but keep swimming in a 

 somewhat spiral mode. The brain, as in the females, is threclobed and of the same shape 

 (though I am of opinion the two smaller lobes are a little more pointed, an<l in some eases 

 slightly more granular or opaque). Eaeh sac is filled with numerous cell.s, which give the 

 covering or skin the appearance of being beautifully and evenly marked with a fine hexagonal 

 pattern. This I have noticed is the case in the female too. The occipital antenna stands at 

 the base of the long lobe of the brain, and I also find this in both genders. The eye is seated 

 on a small ganglion, which rests between the two sides or small lobes, and under the long, 

 narrow neck of the centre lobe of the brain. The cavity of the body, which in the feniale 

 contains the mastax, stomach etc. is fdled with a large empty sac. The lumbar tentacles, with 

 their retractile setæ are the same as in the female. Four vibratile tags run down each side. 

 The large sperm sac and protrusile, ciliated penis are obvious. I noticed the spermatozoa in 

 active movement inside the sperm sac. The size overall is Vbs"." 



Description. Body shaped like that of the female but much more hyaline. 

 The great fat, ventricose, tail highly characteristic of the female is but slightly 

 developed in the male. As in the female the body is short and thick, constricted in 

 the anterior part. The wheel-organ consists of a rather vertically situated convex disc, 

 surrounded by cilia and two large auricles which, in contradistinction to the female, 

 are almost always extruded. On the disc stand some bunches of long bristles; there 

 is no lip. The brain is large, bilobed, carrying a large red eye and gives nerves to 

 the dorsal antenna and the two lateral antenna?, lying in the posterior part of the 

 body. The tips of the tubules carry strong setæ (this according to Gosse is not the 

 case with those of the female). Just as in the female the retro-cerebral organ is 

 highly developed, consisting of a large median lobe, constricted in front, and an- 

 teriorly with two much smaller lateral lobes. The interior of the large sac is filled 

 with a great quantity of vacuoles, often, owing to the pressure, almost penta- or 

 hexagonal. As staining methods have not been used I cannot give a more thorough 

 description of the organ; the ducts and the openings for the organ I have not been 

 able to detect. The so-called "granulations calcaii'es or bacterioides" (ue Be.xuchamp) 

 may be present, but may also be almost wholly absent. Of the alimentary canal 

 there is only a rudiment between testis and wheel-organ. Lateral canals strongly 

 curved with five or six vibratile tags. There is no contractile vesicle; the openings 

 of the canals at the tip of the penis have not been seen. The testis is exlremely 

 large, almost globular, often placed laterally. The penis itself opens on the posterior 

 border of the last segment; it is protrusile and the canal is covered with cilia; a 

 bundle of cilia at apex; there are two large prostata glands and two large pedal 

 glands. There are seven transversal muscle-bands, at all events four longitudinal 



31* 



