32 ZOOLOO T. 



tion is then carried on by the help of the lip alone, which 



expands latterly until it 

 completely overlies the 

 particle. All this is done 

 quite rapidly, in a few sec- 

 onds, and then the food 

 glides quickly into the 

 depths of the body, and is 

 enveloped in a digestive 



Fig.20.-Monad 8 (Cr^a).-AfterTuttle. yacuo l e? whilst the lip ES- 



sumes its usual conical shape and proportions. " (Clark.) 

 All the monads have a contractile vesicle. In Monas 

 termo, Clark observes that it is " so large 

 and conspicuous that its globular form 

 may be readily seen, even through the 

 greatest diameter of the body ; and con- 

 tracts so vigorously and abruptly, at the 

 rate of six times a minute, that there 

 seems to be a quite sensible shock over 

 that side of the body in which it is em- 

 bedded." The contractile vesicle is 

 thought to represent the heart of the 

 higher animals. The reproductive organ 

 may possibly be represented in Monas 

 termo by a "very conspicuous, bright, 

 highly refracting, colorless oil-like globule 

 which is enclosed in a clear vesicle" called 

 the nucleus. This and other monads live 

 either free or attached by a slender stalk. 

 As an example of the compound or aggre- 

 gated monads may be cited Uvella, prob- 

 ably glaucoma of Ehrenberg. Other 

 forms, as Codosiga, are fixed by a stalk to, 

 some object (Fig. 21, C. pulclierrimus 



1 -v T J.T j n- i Fl g- 21. A, Codostqa 



Clark). In this and allied forms the body, putilUrrimw. B, the 



is surmounted by a collar or calyx out 



which the flagellum projects. The Qo : - 



dosiga has been observed by Clark to.uii- als -" Afte;r Clark - 



dergo fission, two independent monads resulting, within the 



space of forty minutes. 



