252 64 



Characteristic of all hitherlo observed males is their conical shape, their often 

 short foot, with two toes and well-developed foot glands. The wheel-organ is simp- 

 lified to a terminally placed disc, surrounded by cilia, carrying on the disc the same 

 four long hairs which characterise the females; auricles are absent and fleshy pro- 

 tuberances only observed in one species. A retrocerebral organ has not hitherto been 

 observed; most probably dorsal as well as lateral antennæ are always present. Below 

 the large brain a large red eye. Rudiment of alimentary canal hollow and often 

 containing globules, most probably present in all species; it has hitherto mainly been 

 overlooked, but it seems to have been observed by Lie Petersen in S. iwrax; some 

 of Rousselet's figures seem to show rudiments of the alimentary canal. Whereas 

 Plate (1886, p. 45) states that the length of the excretory canals in the females is 

 very different, Rousselet (1902, p. 272) maintains that they always are very short 

 in the male sex, not extending much over the anterior end of the gastric glands. In the 

 males examined by me I have seen them reaching the brain. The testis is large, 

 pearshaped; there are two short prostata glands; the penis opens dorsallj': it is short 

 and round, the opening provided with short hairs; the muscle system, especially the 

 transversal muscles are highly developed. 



Polyarthra platyptera Ehrbg. 



Male: Gosse 1856, p. 320. 

 Plate 1886, p. 18. 

 Tab. Ill, fig. 3-4. 

 GossE (1856, p. 321, PI. XV, fig. 27 — 29). The small drawings give the figure very well and 

 the comparison with a Vorticella is really excellent. Gosse saj's that the head is very large, 

 with the body tapering quickly to the posterior part; both extremities are truncate. The front 

 bears two warts, between which the rotatory cilia are placed, but the cilia (perhaps setæ) 

 are longer on the warts. The hinder part is bifid, the smaller division being the caudal ex- 

 tremity or toeless foot, and the larger a protrusile truncate penis, ciliated at the tip. No internal 

 organisation is discoverable. In one there was a globule in tlie middle of the great head. 

 Towards the posterior dorsal parts a few irregular dark specks were visible, but generally the 

 whole animal was clear, colourless, highly refracting, and showing an indistinct granulation. 

 Its motions were swift and impatient, gliding atiout the field at headlong speed, occasionally 

 remaining in one place for a few minutes, but not in stillness, for it was rapidly oscillating 

 to and fro, and c|uivering. 



Plate (1886, p. 18, Tab. I, fig. 4) describes the male mainly as follows: 



"In ihrer Gestalt weichen sie durchaus von den Weibchen ab und entbehren, wie fast 

 alle Rädertiermännchen, einer Mundöffnung und eines Kauapparates. Die flossenartigen An- 

 hänge des Weibchens fehlen völlig und auch von einem Augenfleck ist nichts am Gehirn zu 

 erkennen . . . Die Männchen lassen eine Bauch- und eine Rückenseite unterscheiden, von denen 

 diese etwas schmäler ist als jene. Beide hängen durch zwei nach innen gebogene Seitenflächen 

 mit einander zusammen. Nach hinten verjüngt sich der Körper in den Penis, der am freien 

 Ende bewimpert ist und während des Umherschwimmens teilweise eingezogen wird. Ein Fuss 

 an den sich der Penis nach Gosse ansetzen soll, ist nicht vorhanden. Vorn bildet der Körper 

 einen halbkugelig vorspringenden, einstülpbaren Kopf, der mit einem einfachen Cilienkranze 

 und innerhalb desselben mit 2 Büscheln starker Wimpern besetzt ist. Der grösste Teil der 



