INTRODUCTION. 31 



esteem its refutation unworthy of his pen, and a Harvey- 

 thought it necessary to record his dissent from it and his 

 behef that the pheenomenon must be regarded as a " strictly 

 vegetable peculiarity." All that I have alluded to as hap- 

 pening in the Algae occurs also in the Desmidiese ; but no 

 similar motion has ever been observed in the contents of an 

 animal after their escape from the individual, and I there- 

 fore claim its presence in the Desmidieee as a strong pre- 

 sumptive evidence in support of their vegetable nature. 



Starch has been observed in the Desmidiese by many per- 

 sons, and I am not aware that its occurrence is now denied 

 by any one. I should therefore have supposed that it hardly 

 required further proof, but as the subject is altogether un- 

 noticed by most writers on the opposite side, it becomes 

 necessary to bring it fully before the reader. 



Meyen first directed attention to the presence of starch as 

 a conclusive proof that the Desmidiese are Algse. He states 

 that in several genera he has " distinctly seen that the large 

 and small granules contained amylum, and were sometimes 

 even entirely composed of it*," and that " in the month of 

 May he had observed many specimens of Closterium in 

 which the whole interior substance was granulated, and all 

 the grains gave with iodine a beautiful blue colour, as is the 

 case with starch, which is not an animal product.^' I know 

 not that Ehrenberg or his followers have ever repeated 

 Meyen's experiments or taken the slightest notice of them, 

 important as they are to the solution of the disputed ques- 

 tion. In this country, Mr. Dalrymple at first failed to detect 

 starch in the Closteriae, but afterwards observed it in spe- 

 cimens of Closterium (Penium) Digitus, which I sent him, and 

 acknowledged its presence in the following terms : — " I have 

 examined the specimens sent up, and in several I can detect 

 the blue colour of the iodide of starch ; this is by no means 

 however universal, some being merely stained yellowish- 

 brown ; but in those instances there appears to be an absence 



* See American Journal of Science and Arts, vol. xli. p. 298. 



