Megalotrochaea.'] infusorial animalcules. 615 



organ has two lappets. The nutritive system consists of a stomach, 

 caecum, rectum, and oesophageal head, having two jaws, with teetli, 

 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 oesophageal. The eyes are frontal, of a red colour 

 wdien young ; two, many-partite, radiant nervous masses are dis- 

 tributed in the disc of the rotatory organ ; these represent the 

 nervous structures and organs of sensation, four circular transverse- 

 lying vessels (muscles?) are also seen. The nature of the four opaque 

 white spherical bodies at the base of the rotatory organ is unknown. 

 Megalotrocha albo-Jlavicans {Vorticella socialis, M.) — ^White and 

 free, when young ; yellowish, and attached in radiating clusters, when 

 old. Ehrenberg states he has often perceived the red eyes within 

 the unbroken egg, 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 egg, when expelled from the body, re- 

 mains attached to it by a thread, and the parent has often four or 

 five thus attached, and in process of further development. Ehren- 

 berg' s observations on the embryo are highly interesting : he says, 

 " In the ovum, whilst within the ovarium, a bright germ makes its 

 appearance as a round clear spot ; within this a turbid nucleus 

 developes itself, which at first is surrounded with a bright broad 

 margin of fluidity; within the nucleus a central pellucid vesicle, 

 like a yolk, is gradually developed ; the ovum is then expelled. 

 The embryo is now quickly developed within the vesicle of the 

 nucleus or yolk, and becomes visible when this latter is consumed ; 

 a turbid central spot then appears, which becomes the oesophageal 

 bulb and teeth ; a blackish granular oval body is also seen pos- 

 teriorly, the eyes gradually become red, and a motion of the cilia is 

 visible : after some hours the whole foetus, which is folded up, 

 turns itself round, the shell bursts, and the young animalcule 

 creeps out ; it then fixes itself between the older ones, but in a 

 little time the young creature detaches itself and swims about as a 

 rolhng sphere, and at the expiration of a certain period attaches 

 itself to some firm body." Figs. 374 to 3/6 represent diff"erent 

 specimens ; fig. 377 merely the teeth and jaws separate. Found 



