23 211 



tion deriving from Burmeister and Leydig and still maintained by Hudson-Gosse, 

 that the Rotifera were Arthropoda, either related to Crustacea or Insects, caused 

 Pedalion, when found, to be referred to a special order, showing special affinity to 

 the Arthropoda (v. Daday 1886 p. 214). In all essential points the system was adopted 

 by Plate (1891 p. 320) who only introduced the apparent and commonly adopted im- 

 provement: The removal of the Philodinidæ and Seisonacea as Digononta in contradiction 

 to all other Rotifera (Monogononta). Especially after Claus (1895 p. 1) and Levander 

 (1894 p. 32) had shown that Pedalion had no Artropod characters at all, the old 

 supposition, that the Rotifera showed affinity to the Arthropoda, was abandoned, 

 but nevertheless the systematical arrangement of Hudson-Gosse was still preserved 

 and mainly used in Deutschlands Süsswasserfauna (1912) as well as in Weber's 

 (1898) and Montet's (1918) treatment of the Rotifera in Switzerland. A great 

 improvement was made by Hartog (1910 p. 220) who separated the Rhizota into 

 two orders, Flosculariacea and Melicertacea, otherwise the system of Hudson-Gosse 

 was preserved rather unaltered. This rather persistent adherence to this system, 

 was mainly due to the fact that the Rotifera, almost simultaneously with their 

 happily escaping affinity whith the Arthropoda, owing to a superficial resemblance 

 between some Rotifera, especially the Trochosphæra just detected at that time and 

 the Trochophora larva, were regarded either as forerunners of the Annelida (Semper 

 1872 p. 305, Hatschek 1878 p. 100 a. o.) or as larvæ of Annelida which have arrived 

 at maturity, neotenic Annelidalarvæ (Lang 1888 p. 186). It will be clearly under- 

 stood that this view can only be adopted when the typical wheel-organ is regarded 

 as two ciliary wreaths, corresponding with those found in the Trochophora larva 

 and must be totally abandoned, if the ventrally placed, cilia-coA'ered disc is regarded 

 as the typical one. As mentioned, already in 1899 I found the comparison with 

 the Trochophora larva and the attempt to connect the Rotifera with the Anne- 

 lida to be a total mistake, almost just as great as the attempt to connect them with 

 the Arthropoda. The Rotifera are nearly connected with the Turbellaria, in which 

 I am inclined to see their nearest allies. As far as 1 understand, this is also mainly 

 the opinion af de Beauchamp (1900 p. 56), who especially seems to lay stress upon 

 the Gastrotrica as the connecting link between the two groups. 



Before entering upon the description of the males I think it most reasonable 

 to give a short sketch of my views on the relationship between the families. My 

 systematical views, set forth in 1899, have been criticised by de Beauchamp who, 

 even if he is in accordance with me on many points, in many others differs con- 

 siderably from me. De Beauchamp has summarised his criticism in the following 

 sentence "II (W-L) a pressente les vrais rapports dans les cas, ou il les a énoncée, 

 plutôt qu'il ne les a démontrés". This remark, is indeed quite correct. As it may 

 most probably be used as a motto over almost all my papers, as well as over all 

 zoological work, carried on in Nature herself and performed upon the basis of 

 thoughts and ideas which have arisen during the excursions themselves, more from 



