THE BEGINNINGS OF LIFE. 439 



pendent unit, all of which soon begin to exhibit slight 

 signs of movement (/). The united movements of the 

 contained units soon rupture the delicate investing 

 membrane, from which they emerge as small but active 

 flagellated Monads or Zoospores. They appear as al- 

 most transparent spheres about -g-gVir" in diameter, each 

 of which contains a large nuclear mass at its posterior 

 extremity, and swims by means of the vibration of a 

 single anterior flagellum 1 . Their ultimate fate will be 

 subsequently referred to 2 . 



Under, less favourable conditions these nucleated 

 vesicles are not liberated as flagellated Monads, but 

 as motionless corpuscles, which also protrude motion- 

 less, ray-like prolongations, capable of enlarging into 

 tubular filaments and branching in various directions. 

 They grow, in fact, after the fashion of a Fungus-germ ; 

 and the nuclear mass within the germinal vesicle 

 becomes subdivided into two or three smaller portions, 

 whilst the vesicle itself enlarges. Wherever the fila- 

 ments issuing from these bodies come into close con- 

 tact with Euglenae, they seem to penetrate j and, by 

 virtue of some more coercive molecular movements, 

 or vital changes, they gradually alter the constitution 

 of the Euglena itself, so as to make it also take on 

 the fungoid mode of growth. 



1 Dr. Gros has evidently seen a similar change take place (see loc. 

 cit., p. 312, PL D, figs. 13-16, 21). And, although he does not 

 expressly state that the Monads arise in an outgrowth, he has in 

 other parts of his memoir spoken of the formation of such outgrowths. 



8 See p. 472. 



