THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. XII. JULY, 1891. STo. 7. 



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Some New and Little-known Rotifers.* 



By W. BARNETT BURN, M. D. 



[with frontispiece.] 

 PHII.ODINA TUBERCULATA. 



This rotifer, shown in Fig. i, is of large size, and occurs frequently 

 in pools, yet it is not well known, and I do not think has been figured 

 before. It is curiously like the Rotifer tardus., though in important 

 points so different ; whereas, though in all essential details coming 

 very near Philodina aculeata, in aspect it is quite dissimilar. 



In considering the points of resemblance of this species with Rotifer 

 tardus^ we notice the general outline, the brown color, the deep folds 

 in the body, the proportion of the width of the wheels to the neck, and 

 the habits and movements of both are the same ; also the toes are some- 

 what alike, but here we come to the distinctive chai^acterof Philodina 

 tuberculata ; it differs from all its relatives in its long and slender 

 spurs, and by this alone it may be recognized. Rotifer tardus ap- 

 proaches nearest to it in this particular, but the spurs are thicker, and 

 the toes longer in proportion to them ; in the former the last joint of 

 the foot comes down over the toes, acting as a sucker, and, in doing so, 

 flattens out, giving the appearance of the animal having four or five 

 toes. Then there is the radical difference of the position of the eye, 

 being in the rotifer in the frontal column and in the philodine in the 

 neck ; also, the former has only two teeth each side ; the latter has three 

 teeth on one side, if not on both. Sometimes many will be found 

 having only two teeth on one side. I have counted sixty in succession 

 with this peculiarity, and at other times have seen three on both sides 

 always. Lord Osborne, who specially studied the teeth of rotifers, ob- 

 served the same variation in Philodina roseola., and other observers in 

 other species. It may be a case of knowledge comingand wisdom lin- 

 gering, the third tooth being cut late in life when versed in the ways of 

 the world. 



*Science-Gossip. 



Copyright, 1891, by C. W. Smiley. 



