505 



Further Observations on Male Kotifers. 



By K. I. Marks, F.H.M.S., and W. Wesche, F.R.M.S. 



{Read April \1th, 1903.) 



Plate 26. 



We are now able to add to the list of male rotifers two 

 species which have not been previously observed, Brachionus- 

 quadratus Rous, and Anuraea hrevis2n7ia Gosse, and to furnish 

 particulars of another, Pterodina patina Ehr., a very well 

 known and common species, the male of which has been recorded, 

 but not figured or described. 



The males of two of these species were obtained from a pond 

 adjoining Willesden Lane, which, if one may judge from the trees 

 growing on its banks, must be of very considerable age. During 

 the last twelve months this pond has invariably yielded B. 

 quadratus in considerable quantities. Several males were seen 

 swimming in company with the females, but to prove their identity 

 a female with four male eggs was isolated, and the drawings now 

 submitted were made from the males hatched out from these 

 eggs in the course of the following night. This male has been 

 observed to spin a thread from the toes, and anchor himself by it,, 

 an action seen also in the male of B. angularis. In all the known 

 males of Brachionus there is present an organ the explanation of 

 which is a matter of considerable difficulty. It consists of a mass 

 of blackish granules enclosed, in some instances at least, in a 

 separate membrane, and situated on the dorsal side immediately 

 above the sperm-sac. This mass not only differs in appearance in 

 different species, but is very variable in shape in individuals of the 

 same species, whilst it occasionally appears broken up, a portion 

 being seen in another part of the body. It has therefore no value 

 as a specific character. Gosse * noticed this granular mass in all 



* Phil. Trans., vol. 147, 1856, p. 324. 



