216 28 



been altered in accordance with variation in life conditions, will never be able, 

 because of his investigations, to return to this system. I only wish to add that even 

 if I have been forced to attack the system of the learned English authors, my ad- 

 miration for what these two Scientists have done to promote science in this 

 difficult domain of natural history, has in no way been abated. It will always be 

 the work to which all students of this group of animals will return ; in my opinion 

 this is mainly due to the excellent and exact contour drawings of the animals, which 

 only rarely give room for doubts with regard to the conception of tlie animals which 

 the authors have described. 



3. With regard to my arrangement of the Rotifera in developmental lines, starting 

 from the Xotommatidœ, it is with the greatest interest I have seen that de Beauchamp 

 has arrived at quite the same result for some of them. This especially holds good 

 for the line Xotommatidœ, Hydatina, Xotops brachioniis, Brachioniis and Anurœa. 



I suppose that it is quite correct, as de Beauchamp has done, to separate the 

 Ploesomatidœ from the next line, consisting of Triphylus, Harringia, Asplanchnopas 

 and Asplanchna. Nearly related to it, is the small developmental line of Xotops 

 hyptopus. Ploesoma. Gastropus and perhaps Anapus, a line which begins in the No- 

 tommatidæ, especially with forms related to Copeus. 



The Synchœtadœ which are taken by both of us with quite the same restrictions, 

 are in my opinion nothing but Xotommatidœ that have emancipated themselves from 

 a substratum; they are closely associated with the Xotommatidœ through such spe- 

 cies as .V. aurita and A', pilarias. Researches from recent years show that the last 

 stages in this developmental series show structures very similar to those which we 

 find in the genus Asplanchna (balloonshape, peculiar humps etc.). See especially 

 Plate (1SS9, p. 1), Levaxder (1895, p. 21), Rousselet (1909, p. 170). 



The lines comprising the old loricate families Rattutidœ, Diaschizadœ, Euchlanidœ, 

 Coluridœ, Dinocharidœ and Cathypnadœ cannot be drawn with such great certainty as 

 the above-named; in the Xotommatidœ-Rattulidœ and in the Xotommatidœ, Diaschiza, 

 Salpina, Euchlanidœ I see two different developmental lines. The genera may perhaps 

 be arranged in a somewhat different way, and the families Coluridœ, Dinocharidœ 

 and Cathypnadœ placed in this great division. All in all this does not obviate the 

 greater difficulties of the systematic view which is advanced here, and de Beauchamp's 

 arrangement may most probably be said to come as near to the truth as possible; 

 great differences between his results and mine do not seem to exist. 



Upon all these points there is no doubt that de Beauchamp has given my 

 views upon the systematical arrangement of the Rotifera that scientific basis which 

 they most certainly lacked, and upon many points he has introduced improvements. 

 Some of the most aberrant families, the Trochosphœridœ and Seisonacea, are still 

 without any systematical connection with the other Rotifera, and for my own part 

 I am doubtful as to whether the Seisonacea may be referred to the Rotifera at all. 



With regard to the Bdelloida de Beauchamp is in doubt as well as myself as 

 to whether the placing of them and the Seisonacea in a special division, Digononia, in 



