No. 548] A CASE OF POLYMORPHISM 443 



ciliated corona in a very conspicuous fashion. When it 

 met one of the ofcher rotifers in a head-on collision it was 

 much less inclined to contract or turn a quick somersault 

 than was the companion type. As to the specific, 

 varietal, or other classification of this large campanulate 

 Asplanchna I could find nothing. I concluded that it 

 must be an as yet undescribed species. Its distinctness 

 was further borne out by the results of detailed study. 



The characters hitherto most extensively used for 

 specific definition in the genus Asplanchna are size, body 

 form, type and development of nephridium, and the form 

 of the trophi. As to the nephridia of the two forms in 

 question, they proved, indeed, sufficiently different. 

 Although built upon the same general type, their size and 

 the number of flame cells bespoke wide separation. 

 Rousselet, who is the first authority upon the classifica- 

 tion of rotifers, in his last article 1 discussing the species 

 of Asplanchna expresses his belief that the number of 

 flame cells is constant in each species, although he admits 

 that it is very difficult to make strictly accurate counts of 

 these delicate organs. He assigns to Asplanchna 

 amphora about 40 flame cells, and this is a much higher 

 number than has hitherto been found in any other species. 

 My preparations permitted much better counts than may 

 be made on the living animal, but still I am not certain 

 of exactness. I found, however, that even the humped 

 rotifers frequently bore about 50 flame cells on a side, 

 and in many instances I found 55. In the campanulate 

 type the number was astonishingly greater. Not only 

 was the nephridial tube bearing the tags longer, stretch- 

 ing from the knotted portion near the bladder in a wide 

 diagonal curved line to the lateral edge of the corona, but 

 it was very thickly studded throughout the greater por- 

 tion of its length with the flame-bearing tags. The 

 number was certainly variable in larger and smaller 

 specimens, but it was frequently about 100, and in a 



QvecTc. Mic. Club, Second Series, Vol. VIII, pp. 7-12. 



