340 DESCRIPTION OF {Rotatoria. 



become effaced by age. The rotatory organ has two lap- 

 pets ; the nutritive system consists of a stomach, coecum, 

 rectum, an oesophagal head, having two jaws, with teeth, 

 and two pancreatic glands ; reproductive organs, a short 

 knotted ovarium, with a few ova ; muscles, three pair 

 anterior, two pair posterior longitudinal, two contractile 

 muscles for the rotatory organ, and four oesophagal. The 

 eyes are frontal, of a red colour when young ; two many- 

 partite radiant nervous masses are distributed in the disc 

 of the rotatory organ ; these represent the nervous struc- 

 tures and organs of sensation, and four circular transverse- 

 lying vessels are also seen. The nature of the four opaque 

 white spherical bodies at the base of the rotatory organ is 

 unknown. 



573. Megalotrocha cr/fto^avaows {Vorticella socia- 

 lis, M.) The yellowish-white Megalotrocha is white and 

 free, when young, yellowish and attached in radiating 

 clusters when old. Ehrenberg states he has often per- 

 ceived the red eyes in the closed ovum, and the jaws, as if 

 in the act of chewing, move laterally and horizontally against 

 each other. Two ova are rarely produced at one time ; the 

 ovum, when expelled from the body, remains attached to it 

 by a thread, and the parent has often four or five thus 

 attached, which are thus further developed. Ehrenberg's 

 observations on the embryo are highly interesting: he says, 

 " In the ovum, Avhilst within the ovarium, a bright germ 

 makes its appearance as a round bright spot ; within this a 

 tiurbid nucleus developes itself, which at first is surrounded 

 with a bright broad margin of fluidity ; within the nucleus 

 a central bright vesicle, like a yolk, is gradually developed ; 

 the ovum is then expelled. The embryo is now quickly 



