BRACHIONUS QUADRATUS, AND BRACHIONUS RUBENS. 153 



exploitation of the obvious advantage of riding, free of charge 

 and without exertion, on a Daphnia's back appears to show a 

 higher education and greater intelligence in B. rub ens (or perhaps 

 a lower type of morality as suggested by Mr. Scourfield) than in 

 B. urceolaris. Various free-swimming Rotifers occasionally and 

 temporarily attach themselves to water-fleas ; but I know of only 

 one species other than B. rubens that does so systematically, 

 namely, Proales daphnicola, Thompson. 



Brachionus rubens is not a very common species. I have 

 found it occasionally around London, particularly in a pond at 

 Totteridge, and have had it sent to me from Kent and other 

 parts in the country, always associated with Daphnia. 



Both Dr. Hudson and Mr. Gosse appear never to have become 

 acquainted witht he true B. rubens. I once showed Dr. Hudson 

 some mounted specimens and pointed out their agreement with 

 Ehrenberg's drawings, and their disagreement from Mr. Gosse's 

 figures. His reply was that the only explanation he could give 

 was that the published figures had been selected by Mr. Gosse 

 from numerous sketches in his possession as the ones coming 

 nearest to those of Ehrenberg ; he quite agreed that Ehienberg 

 was correct and that his figures of B, rubens ought to be taken 

 as representing the true species. 



From what has been said it follows that in Hudson and 

 Gosse's monograph, fig. 5, pi. xxvii., and also the figures of 

 Plate A, must be taken to represent B. urceolaris and not 

 B. rubens. 



Fig. 9 of PI. 12 has been very carefully drawn to show the 

 usual shape of the frontal teeth of the true Brachionus rubens, 

 but these teeth are subject to individual variation. Fig. 10 is a 

 drawing from a photograph by Mr. W. Imboden of a mounted 

 specimen under dark-ground illumination, whilst Fig. 11 

 represents the male drawn by Mr. F. It. Dixon-Nuttall. The 

 resting egg is of a light brown colour, elongate, broad at one end 

 and obtusely pointed at the other, enclosing a nearly spherical 



