THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY 



[SECOND SERIES.] 

 No. 9. SEPTEMBER 1848. 



XIV. — Some Account of a dioecious Rotifer allied to the genus 

 Notommata of Ehrenberg. By Thomas Brightwell, F.L.S. 



[With a Plate.] 



Notwithstanding the laborious researches of Ehrenberg and 

 other eminent zoologists among the microscopic animals, much 

 obscurity still rests on their precise characters, and their mode of 

 increase and propagation. 



The Rotatoria of Ehrenberg (Systolides of Dujardin) are 

 characterized as androgynous, combining the male and female 

 parts in the same individual ; but the facts we have to adduce go 

 to show that, at least, one of the more highly organized species 

 is dioecious ; and that it is propagated by a union between the 

 sexes, analogous to that of animals placed in a much higher 

 class. 



It appears that M. Doyere has discovered male organs and 

 spermatozoa in the Tardigrades, a family few in species, but 

 composed of two or three distinct genera. They are incorporated 

 by Dujardin among the Systolides, and form, according to this 

 author, a passage from the Systolides to the Helminthidcs on 

 the one hand, and the Annelides and Arachnides on the other. 

 In like manner the animal we have to describe may perhaps be 

 found to connect this order with the Tunicata by some of the 

 minute free gelatinous animals placed in this class. 



We first discovered this animal six or seven years since in 

 a small pond in this neighbourhood. It is found for a few weeks 

 only, in the warmest weather, and in some seasons it disappears 

 altogether. Last summer, and in other years, not a specimen 

 could be found, but this year (1848) it has appeared rather 

 plentifully. 



The female (see PI. VI. fig. 1) bears a general resemblance to 

 Notommata Syrinx and N. clavulata of Ehrenberg, but it is 



Ann. $ Mag. N. Hist. Ser. 2. Vol. ii. 11 



