Infusoria. 3165 



On Notommata parasita, a Rotifer inhabiting the Volvox globator. 

 By the Rev. R. C. Douglas, M.A. 



Although the following observations add little or nothing to what 

 is already known of this remarkable parasite, they may perhaps be 

 thought not unworthy of notice, as relating to a chapter of microsco- 

 pic life seldom observed in this country. Last summer a paper on the 

 subject was read before the Microscopical Society of London, (Zool. 

 viii. 2891), and has been published in the last part of the Society's 

 1 Transactions.' 



On the 28th of May last, I gathered some Mougeotia genuflexa, 

 from a pond about a mile and a half from Stafford, and on my return 

 home transferred it to a wine-glass. Next morning I saw that the 

 water was full of Volvox globator, but I did not examine any speci- 

 mens microscopically, until the evening of Saturday, May 31st. The 

 globes of the Volvox were then in active motion, and my attention 

 was soon arrested by sundry oval bodies inside several of the globes ; 

 while examining these, a Volvox came across the field of the micro- 

 scope, containing a Rotifer with cilia vigorously at w T ork; this, 1 per- 

 ceived, was the Notommata parasita, and at once conjectured that the 

 oval bodies which had first attracted my attention might be eggs. 

 Presently another Volvox came in sight, also containing a Rotifer. 

 The two Volvoces were not full grown, but the parasites were of large 

 size ; their length, when fully extended, being about two-thirds of the 

 diameter of the containing Volvox. They appeared perfectly indiffe- 

 rent to the motions of the Volvox, either floating freely within the 

 globe, or holding on by their tails and allowing themselves to be car- 

 ried round with it, their cilia all the time in active motion, the work- 

 ing of the gizzard, and the spot or " eye " being distinctly visible. 

 Altogether it was an object of remarkable beauty and great interest. 

 Patches of the surface of each Volvox were without the green gem- 

 mules or animalcules, but I could not detect the parasites actually 

 devouring them, although in one globe a gemmule was partially de- 

 tached, and was knocked about in the current made by the cilia of 

 the Rotifer. The young globes which are generally found within 

 specimens of Volvox, were absent in one case, and in the other were 

 represented by one small fragment. Scarcely any Volvoces were seen 

 entirely free from the parasite, although this evening I only observed 

 two fully developed Notommata, one in each of the globes that were 

 the subjects of the above observations. In many of the larger globes 



