4i6 



THE BEGINNINGS OF LIFE. 



passed through one or other of various changes. Occa- 

 sionally two or three of them^ after having very shghtly 

 increased in size, became ovoid and rather paler at 

 one extremity, before protruding a flagellum and 

 moving about actively as green Monads. Other of the 

 ovoidal corpuscles continued to increase in size, at the 

 same time becoming more and more fusiform, whilst 



- \ 



their green contents became granular [g-y). The 

 most elongated of these were subsequently bisected 

 by a delicate partition; they also developed a greenish 

 nuclear-like body in each segment, and soon began to 

 grow into unmistakeable filamentous Desmids, of which 

 many otherwise similar specimens were seen in all 

 stages of growth {h'-k). But other representatives of the 

 minute ovoid corpuscles assumed a paler colour, and 

 then a slightly olive tint, whilst their colouring matter 

 became in part metamorphosed into two comparatively 

 large, rounded, nuclear corpuscles. These bodies in- 

 creased in size, and it soon became obvious that 

 they were young Naviculse (/,/'). The exact pattern 

 assumed in the early stages is subject to much varia- 

 tion, and several different kinds of Diatom.s seemed 

 to be produced corresponding to these different initial 

 forms {m^ m). At first no striation was observable, 



radually their envelope became more and mor 

 differentiated — silica appearing to be assimilated from 

 the water in which they were immersed — and some ot 



but g 



Q 



^ 



** 



these Diatoms exhibited a well-marked striation. 



r 



Occasionally the individualizing contents of one of 



H 



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II 



ii 



m 



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t^k 





i !' 



Modes of Ori^' 



^fcnalgoidcorpuides 

 Ws from a Cladoj 



, fertile B— id h 

 surror ^^a bv 



IS 



also 



X 





X 



II. 



^niids 



