29 217 



contradistinction to all other Rotifera is really correct (Plate). Along quite dilTerent 

 roads we have arrived at the same results, he starting trom the wheel-organ af Adi- 

 neta and I especially from the behaviour of the creeping Diqlena. In the present state 

 of our knowledge I suppose il is impossible to come nearer lo the truth than de 

 Beauchamp gives it (1909, p. 36). "On ne s'aurait donner' les Notommatides comme 

 ancêtres aux Bdelloides, mais le rapprochement nous éclaire beaucoup, plus même 

 que celui de Zelinka avec Rhinops, d'ailleurs soutenable avec les mêmes réserves, 

 sur la morphologie de l'extrémité céphalique des Philodinidés." Adineta as well as 

 Microdina paradoxa show structures which further seem to strengthen this view. 



Because of insufficient knowledge with regard to the dorsal organ and lateral 

 organs and in consequence of the presumed want of a contractile vesicle Plate 

 (1887, p. 258) has been inclined to see in the Pterodinidœ a family which was related 

 to the Philodinidcc. Owing to great resemblances in the mouth parts (malleo-ramate 

 and ramate) and in the wheel-organ, I confess I have shared this view. As however 

 RoussELET (1898, p. 24) has shown that a dorsal antenna is present, that the lateral 

 antennae are only placed further forward than in most of the other Rotifers, and 

 has further pointed out the existence of a contractile vesicle, I admit that this view 

 cannot be maintained. As further he has described the very peculiar Brachionus ptero- 

 dinoides from Devil's Lake, North Dakota (1913, p. 59), which really seems to be 

 related to the Pterodinidœ, it is perhaps most correct to refer this familj' nearer to 

 the Brachionidœ. 



With regard to the Rhizota, de Beauchamp and I take quite different views, 

 and upon this point I cannot alter the systematical arrangement set forth in 1899. 

 The order Rhizota is onlj' established owing to the common stamp which, every- 

 where in the animal kingdom, and quite especiallj' among fixed animals, common 

 modes of life set upon the organisms. The characters of the order given by Hud- 

 soN-GossE are: ''Fixed when adult, usually inhabiting a gelatinous tube, excreted from 

 the skin: foot transversely wrinkled, not retracted within the body, ending in an 

 adhesive disc or cup" (1889, p. 43). Later authors (Collins, Weber) have certainly ex- 

 panded the description of the order, but as far as I can see, they have not augmented 

 the characters which should justify its establishment. If the description of Hudson- 

 Gosse is altered a little with regard to the sentence "foot transversely wrinkled", it 

 will be seen that it may be used as a characteristic of many groups of fixed animals 

 (f. i. fixed Infusoria), and it will be understood that all these characters are wholly 

 adaptive. The Rhizota contain species with the most different wheel-organs, one wreath 

 of cilia, two wreaths of cilia, no wreath at all; the greatest possible differences in 

 the structure and form of the coronal disc; the placing of the cilia and their struc- 

 ture. The mouthparts are malleate, malleo-ramate, and uncinate; the buccal orifice 

 placed centrally and ventrally; the anus ventrally, terminally or dorsally, often situated 

 high up upon the dorsal side, the rest of the alimentary canal of the most different 

 structure. In the arrangement and structure of the lateral organs the differences are 

 also great. 



