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main lines may be said to be abnost congruent witb mine. On many essential 

 points he has elucidated the facts, given my suppositions a solid basis, and corrected 

 some of my views that were undoubtedlj' wrong. On the other hand, having for 

 years studied the wheel-organs with his elaborate studies in mind, I feel convinced, 

 that the want of observations of the freeswimming animals has on some points been 

 unfortunate for his views, just as the want of a more thorough anatomical examin- 

 ation has been vinfortunate for my views. 



I have referred the wheel-organs to six different types, of these the first, No- 

 tommatidce, the fifth the Melicertidœ, Pedalionidcv etc. the fourth {Hijdalinida', Brachi- 

 onidœ, Anurœadœ) have many points of contact with those of de Beauchamp. Mj^ type 

 No. 2 comprising the Dinocharidœ, Coluridœ, Rattiilidæ, Salpinadœ, Cathijpnada', Euch- 

 lanidœ, Ploesomatidœ) are by de Beauchamp referred to his tvpe No. 4. This is per- 

 haps more correct, the primitive form Cijrtonia, which is of great significance for 

 the understanding of this group, being unknown to me. Mj' type No. 3 comprising 

 the Sijncha'tada' and Asplnnchnadce is the most erroneous; here the study of the 

 wheel-organ of Eosphora, which was also unknown to me, has shown how the wheel- 

 organ of the" Asplanchnadœ is to be interpreted, and that that of the Synchcvtadce 

 is better connected with his type No. 4. My type No. 6, the wheel-organ of the Flos- 

 cularidœ de Beauchamp also refers to a special type; his attempt to connect it 

 with that of the Melicertidœ is in my opinion a great mistake. 



One of the greatest merits of de Beauchamp is his excellent studies of the 

 retrocerebral organ; just the clear indications of the openings for this organ has 

 made it possible for him to establish his excellent scheme of the general type of the 

 wheel-organ, and find the homologies in the different special types. I am inclined to 

 think that, if my work had been written in another language, it would be manifest 

 that bj' my mode of investigation I have through observation and reasoning arrived 

 at many of those mainpoints in the anatomj' of the wheel-organ in the Rotifera which 

 were only fulh' scientifically elucidated through de Beauchamp's researches. 



Simultaneously with the wheel-organ undergoing very considerable modifica- 

 tions the mouthparts are also modified. Originallj' the mouthparts play a pro- 

 minent part in the procurement of food; in accordance herewith thejr are shaped 

 as prehensile organs, by means of which the food is seized and carried into the 

 mouth. The more the wheel-organ is modified to catch the food, the more too they 

 are altered to be only a masticatorj' organ. Only in the freeswimming families Asplanch- 

 nadœ and Sijnchcetada', where the wheel-organ is only a locomotory organ, the mouth- 

 parts are prehensile or clasping organs. There is really the most conspicuous conformity 

 between the different types of wheel-organs and mouthparts. These last named organs 

 may be referred to two main types, the malleate and the forcipate, those of the 

 mainh' detritus and planteaters and those of the typical animals af prey. Both 

 types are to be found in the primitive forms. The more the wheel-organ during the 

 forming of the secondary wreath of cilia is able to procure food for the animal, the 

 more the significance of the mouth parts as prehensile organs is diminished (the malleate 



