W. WESCHE ON MALE ROTIFERS. 325 



raising the temperature of the water in which the Rotifers were 

 living to that of summer heat, 20^ C = 79 F. The male made 

 its appearance, fertilised the female, which laid the resting egg^ 

 capable of surviving in the dried-up mud of the pond, and in 

 that condition waiting for a rainy day. But as males are often 

 found under ice, and indeed at all seasons of the year, the theory 

 that it is only the heat of summer which gives rise to males is 

 untenable. 



In Mr, Rousselet's list of male Rotifers published in the 

 Journal of the R.M.S. there are 63 species that have been 

 figured and described by their discoverers.* In addition to these 

 there is a further list of 31 species that have been noted, but of 

 which no description or figure has been published. I am now 

 able to figure and describe three species from this second list, 

 as well as a new mastaxed male, several specimens of which 

 were seen by Mr. K. J. Marks and myself, but whose species we 

 were unable to determine, though it seems fairly probable that it 

 belongs to the Notommatadae. 



The first male I have to refer to is that of Triarthra lotigiseta 

 Ehr. It is minute, variable in size, generally inclining to be 

 globose in form. The head is well defined, and its limits are marked 

 by several folds of skin. The body is broad and stout. The foot 

 is well separated from the body, without toes, but with two short 

 setae on the orifice of the penis which goes down to the extremity 

 of the foot. The setae are like those in Syiichaeta, composed of a 

 number of fine hairs. There is a large brain with a conspicuous 

 sub-circular eye-spot. 



Four powerful muscles are attached to the brain and cilia. 

 The cilia are long and fairly strong. The dorsal antenna is 

 connected with the brain by a flexible tube. 



The lateral antennae are well marked, and have the usual 

 tapering gland, noticeable in the female. There is no trace whatever 

 of a digestive system. The lateral canals are well maiked and 

 the contractile vesicle large. The skin is thick but flexible. A 



* Journ. R. Micr. Soc, 18.97, pp. 4—9. 



