218 30 



Already Dujardin but more especially Hartog (1910, p. 220) understood this. The 

 last-named author referred the two families, the Flosculariadce and the Melicertidce, to 

 two different orders Flosciilariacea and Melicertacea. De Beauchamp (1909, p. 32) 

 again refers them to the order Rhizofa, comprising the two suborders Melicertiens 

 and Flosciilariens. H lava (1904, p. 25) has divided the Melicertidce into two subfamilies 

 Melicertiens and Conochiloidiens and de Beauchamp (1908, p. 129) refers them to 

 two different families Melicertidce and Conochiloidœ. Later on de Beauchamp (1912, 

 p. 242), in accordance with the work of Miss Foulke, (1884, p. 37) divides the 

 Floscnlariens into two families, the one comprising the three genera Acyclus, Cupe- 

 lopagis (= Apsiliis) and Atrochus, the other the genera Floscularia and Stephanoceros. 

 The order Rhizota is then according to de Beauchamp divided into two suborders 

 Melicertiens and Floscnlariens, each with the above-named two families. With regard 

 to the standpoint of Hartog and myself he further adds: "II ne faut pas exagérer, 

 comme l'a fait W.-L., jusqu'à nier tout rapport entre ces deux groups et leur en 

 attribuer de très artificiels avec d'autres." (p. 32) In my opinion there is not the slightest 

 affinity between the two great families, each of them is much more closely related 

 to various freeswimming Rotifera than to each other, and as long as this is not 

 clearly understood, these very families cannot be systematically placed. 



Owing to the structure of the mouth parts, the wheel-organ, the form of the 

 bod}', the peculiar "limbs" {Triarthra brachiata Rousselet 1901, p. 143. PI. VIII, 

 fig. 7.) Triarthra and Pedalion may be referred to the same family, Pedalionidœ. This 

 was done by me in 1899 and so far de Beauchamp shares ray views. A close 

 examination will further show great mutual congruity upon all essential points 

 between the Melicertidce, and Pedcdionidce (mouth parts, wheel-organ with two ciliary 

 wreaths). In my opinion Pedalion is a pelagic Melicertid which has preserved the 

 wheel-organ and the mouth parts of the Melicertidce; the changed mode of life as a 

 freeswimming organism has caused the loss of the foot and the peculiarly shaped 

 "limbs". How the two peculiar stylate ciliated appendages in Pedalion are to be in- 

 terpreted, I do not know. 



To see adaptive features due to common life conditions in all these common 

 characters is quite impossible, the one family being fixed, the other consisting of 

 freeswimming plancton organisms, de Beauchamp (1909, p. 29) says: "Par ce double 

 charactère (malleoramate mouth parts and two ciliary wreaths) on a voulu les rap- 

 procher des Rhizotes Melicertiens, qui les possèdent également. J'ai montré que la 

 convergence due à un même mode d'alimentation suffisait à les expliquer." His views 

 have been set forth at greater length already in 1908 (p. 128). Upon this point I quite 

 disagree with the learned author; of course the mode of nourishment is the same in 

 the two families; but whence does this mode arrive, which is common to them 

 both and which, being once elaborated in this form, is unique among the families 

 of the Rotifera. 



Which seems the more natural to suppose, that the combination of malleoramate 

 mouth parts and the two ciliary wreaths showing in all their details the greatest 



