INTRODUCTION. 23 



in fact, he produces no other reason for denying the vegetable 

 nature of some genera. But it will probably be thought a 

 sufficient answer to mention that Meyen and others have 

 proved the growth by elongation and bisection of the 

 cells to be very frequent, if not universal, in the more simple 

 Algae*. 



Meyen remarks that Ehrenberg has interpreted " all the 

 facts known as if these creations were undoubtedly animals, 

 whilst the same facts would indicate quite a different signi- 

 fication if we proceeded upon the supposition that they were 

 nothing but plantsf." In the present instance we have a 

 striking example of the truth of this observation, since 

 Ehrenberg, on observing that division occurs in the lower 

 animals, too hastily draws the inference that only animals 

 can be the subjects of it. 



On the other hand, Mr. Shuttleworth, in a letter to Mrs. 

 Griffiths, written in the spring of 1842, described the growth 

 of the simple Algae by repeated spontaneous division of their 

 cells, and illustrated it by sketches of Zygnema nitidum, &c. 

 He states that the process is most evident in the Oscillatorise, 

 in Conferva fugacissima, in Lyngbya muralis, and in the Con- 

 jugatae ; and, after noticing the similar process in the Dia- 

 tomaceee, he adds, '* I trust that now their vegetable nature 

 is beyond all doubt ;" thus showing that from the same pre- 

 mises two able observers came to exactly opposite conclu- 

 sions. It is right to mention that Mr. Shuttleworth did not 

 claim the credit of being the original discoverer, but merely 

 said that he had convinced himself of the correctness of 

 the facts published. 



To Mr. Hassall is justly due the credit of first directing 

 the attention of British naturalists to this mode of growth ; 



* " The increase by self-division occurs in all these genera ; this process 

 is looked upon by Ehrenberg as one of the strongest and most decisive cha- 

 racters of animal nature ; but I have elsewhere proved, in the most satisfac- 

 tory manner, that self-division is very common, both in the lowest plants as 

 well as in the elementary organs of the more highly developed ones." — Meyen, 

 1839; see Pritchard's Infusoria, p. 180. 



t See Pritchard's Infusoria, p. 178. 



