90 DESCRIPTION OF [Polygastrica. 



for an illoricated and eye-less green Monad. When 

 Monads are assembled, however, in vast numbers, we 

 may, with a little trouble, almost always arrive at some 

 definite conclusion, but with only a single one, or upon 

 a superficial and hasty examination, the genus cannot be 

 accurately determined. 



The only locomotive organ which has been discovered in 

 the Monad genus is the single filiform proboscis issuing 

 from near the mouth. The numerous cilia sometimes 

 apparent thereabouts are nothing more than this proboscis 

 in a state of vibratory or rotatory motion. This organ, 

 Ehrenberg observes, has a twofold office to perform, the 

 one being locomotive and the other to provide the creature 

 with food ; hence I term it a purveying organ. 



The nutritive apparatus is readily seen in some of the 

 species in its natural state (instance the M. guttula and 

 vivipara), without the aid of coloured food; in others (M. 

 termo, guttula and socialis), it may be demonstrated by 

 this means. It consists of several distinct or separate 

 cells (from eight to twenty) which are not all filled at 

 the same time, and which are, for the most part, invisible 

 when empty, but when distended with a limpid fluid, 

 appear like so many lucid vesicles within the creatures. 



The propagative apparatus has been particularly noticed 

 in the species guttula and vivipara. It consists of a vast 

 number of granules formed into a net-like mass, and 

 dispersed generally throughout the creature, and of a com- 

 paratively large spherical glandular body, which separates 

 by the process of self- division. 



Monads propagate also by another method, namely, by 

 a self-division of the creature, either transversely, as with 



