61 249 



day, among some hundred isolated females in Ihe margin of Ihe vessels ncarcsl to 

 the window, I saw numerous males encircling the females and swimming with an 

 extraordinary speed. Most probably the pairing took place during the encircling, 

 lasting only a fraction of a second. 



General remarks. 



The males of the Anurœadœ are mainly characterized by having a rather feebly 

 developed lorica, without facets and thorns of any kind; there is no foot, but an 

 often very long flexible penis which cannot be withdrawn. The wheel-organ carries 

 upon its disc some protuberances, carrying strong bunches of cilia or strong setæ 

 often to a number of four. Any trace of an alimentary canal has never been observed. 

 There is a large brain, most probably dorsal as well as lateral antennæ, but they 

 are only rarely observed. A large red eye; no retrocerebral organ observed. Two 

 lateral canals, but no contractile vesicle. Of great interest is the connection Krätsch- 

 MAR has shown in A. aculeata between the excretory organ and the great oil 

 globule above the testis; the excretory porus medially on dorsum is unique in the 

 kingdom of Rotifera. The large testis opens in a thick penis; the ductus seminalis 

 is covered with cilia; the opening with a bunch of cilia often with two strong setæ 

 at apex. Prostata glands present. A well-developed muscle system, also transversal 

 muscles. Krätschmar has shown that they are striped in A. aculeata. 



Synchætadæ. 



The family comprises the three genera: Synchœta, Polyarthra and Anarthra. 

 The genus Polyarthra was formerly referred to the fam. Trinithrada\ In 1899 (p. 135) 

 I dissolved the familly, referred Triarthra to Pedalionidœ and Polyarthra to Syncha>f(td(V, 

 DE Beauchamp (1909 p. 28) has followed me in this. I still regard Polyarthra and 

 Synchœta as nearly allied; on the other hand in many respects especially with regard 

 to the wheel-organ, the differences are rather great, and after we have studied the 

 structure of the males a little more closely, these differences have been augmented. 



Only the males of Synchœta and Polyarthra are known. Both have been studied 

 insufficiently by Gosse and later on more thoroughly by Plate (Polyarthra) and by 

 RoussELET {Synchœta). 



Synchæta pectinata Ehrbg. 

 Tab. Ill, lig. 1. 

 Male: Description. The body is conical, tapering behind, the skin very soft, 

 hyaline, ending in a sharply defined foot, consisting of one rather large segment, car- 

 rying two short acute toes. The wheel-organ is only a ciliary wreath, encircling a 

 terminally placed disc, covered with very short cilia; on this disc there are four strong 

 hairs; no auricles are found; the two club-shaped prominences in front, so charac- 



