W. WESCHE ON MALE ROTIFERS. 329 



could not be seen. This difficulty was rendered quite insuperable 

 by the animal continually snapping and protruding the mastax, 

 so that the trophi were not quiet for a fraction of a second. The 

 oesophagus was moderately long, and the stomach seemed com- 

 posed of a number of circular organs, in each of which was a dark 

 pellet. The lower end of the stomach was hidden by the 

 spermatheca. The lateral canals were clearly seen, but no 

 contractile vesicle. The spermatheca was so crowded with 

 spermatozoa that only the circular heads of the latter could be 

 made out. The penis had a ciliated orifice. This opening was 

 situated lower down the foot than usual. The size was large, 



Habitat, pond at Neasden, February 7th, 1902. 



Most male Rotifers, as might be expected from their peculiar 

 organisation, are peaceable and inoffensive in disposition. I am 

 sorry to find an exception to the rule in the animal under notice. 

 Mr. Marks had two of this species under observation, and had the 

 following experience, which I give in his own words : — 



" On the 8th February, 1902, I was observing some Floscules, 

 and noticed two male Rotifers, similar to that seen at Mr. 

 Wesche's on the previous evening. I was not able to press either 

 of them sufficiently in the live-box to fix them for accurate 

 observation. They were colourless ; had a mastax, small 

 stomach, lateral canals with several tags. One of them attacked 

 a Floscule, which retreated at once, but the aggressor fixed his 

 mastax to the setae and several times nearly managed to pull the 

 head of the Floscule out of the tube, but was unable to effect his 

 purpose, though he tried for at least five minutes. His move- 

 ments were very lively. He measured y^Q"=158/>t. There 

 were many Rotifers almost similar in appearance to iY. naias in 

 the same water." 



My notes state that the water contained some Notommata 

 collaris, which may possibly be the Rotifer alluded to by Mr. 

 Marks, but I have no evidence, morphological or otherwise, to 

 establish a relationship between the animals. 



