510 K. I. MARKS AXD W. WESCHE 



Head, rather short, without quasi-auricles as in female ; 

 constriction of neck not well marked. 



Body, rather broad, but fairly long ; edge of carapace visible 

 laterally, and two folds on the posterior sides when viewed 

 dorsally. The two muscles, so prominent in the female and 

 used to retract the head, are present and well marked, and best 

 seen on the dorsal view. 



Foot, short, stout, retractile, with a gland at the extremity. 



Toes, none. 



Cilia, moderately long. 



Brain, large, occupying all the head and sending a long process 

 to the dorsal antennae. 



Eyes, two, red and well marked. 



Antennae, all three in the centre of the body, almost in a line. 



Setae, very fine and difficult to make out. 



Digestive system, represented by a hyaline membrane, ap- 

 pearing to be in an atrophied condition. 



Vascular system, faint ; no contractile vesicle seen. 



Generative system, very large ; spermatozoa massed in testis ; 

 orifice of penis slightly ciliated and situated half down the dorsal 

 side of the foot ; no granular masses, as in Brachionus. 



Size, o- Jo^h to yl^yth inch ( = 127 to 135 /x). 



Habitat, pond in Willesden Lane, May 12th, 1902. 



The scarcity of males and the difficulty of observing them is 

 well put by W. T. Caiman,* who states that a period of no less 

 than a hundred and thirty years elapsed between the discovery 

 of the female and the identification of the male of Stephanoceros 

 eichhoiniii. But difficulties do not end with the finding of the 

 male, as its extraordinary activity has produced a curious 

 diversity of observations on the actual sexual act. It has been 

 observed in various ways. Gosse satisfied himself that he had 

 seen a momentary coitus at the cloaca. t Dr. Weber had a 

 similar experience.+ Dr. L. Plate had arrived at different con- 

 clusions, having seen the male of Hydatina senta attach itself 



* Natural Science, vol. 13, July, 1898, p. 43. 

 t Phil. Trans., vol. 147, 1856, p. 317. 



I " Notes sur quelques males de Kotateurs," Rev. Suisse de Zoologiey 

 vol. 5, 1897, p. 98. 



