36 INTRODUCTION. 



occurs in acknowledged Algae as well as in the Desmidiese ; 

 and that nothing which can fairly be compared with it occurs 

 in the animal kingdom. Can either of these assertions be 

 disproved ? Again, it has been seen that starch is abun- 

 dantly produced in this family. Can a single example be 

 referred to where it is an animal product ? I have shown 

 that the reproductive body is formed in a manner well known 

 amongst the Algae, but never detected in animals. Until 

 these facts have been denied, or the arguments deduced from 

 them refuted, I shall presume that the claim of the Des- 

 midiese to be considered vegetables is firmly established*. 



The Desmidieae I regard then as Algae, allied on the one 

 side to the Conjugatae by similarity of reproduction, and on 

 the other to the Palmelleae, by the usually complete transverse 

 division and by the presence of gelatine. Indeed the relation 

 to the latter is so intimate, that it is difficult to say to which 



* Since the above was written, a friend has furnished me with the trans- 

 lation of a passage from a recent work of Meneghini, which is so appropriate 

 in support of my views that I gladly introduce it here : — 



"The Closteria and the Desmidiece are universally plants and not animals. 

 In the actual state of science we are obliged to admit this proposition. The 

 organic structure, the physiological phsenomena, the history of their develop- 

 ment, their chemical composition, manifest in these beings a perfect corre- 

 spondence with others, which, under all their aspects, are comprised in the 

 abstract idea of a plant. On the other hand, what they present in common 

 with those beings evidently animal is but an appearance, or at most a simi- 

 larity of external form. Ehrenberg was deceived by this appearance, and, 

 guided by this fallacious resemblance, thought he discovered even in the 

 Desmidieae the same organic peculiarities which prove the animallty of other 

 beings. What must we infer from this ? That even the most accurate ob- 

 server and man of genius may err. This can never diminish his merit or 

 render less important the services which he has rendered to science. The 

 loss will fall only on those who, averse to the fatigue of observing, content 

 themselves with the authority of the master, and embrace without distinction 

 his real discoveries and his errors. Thank Heaven, the epoch of authority 

 is passed, and whoever submits to its yoke may be allowed to err, because 

 science will not advance the less for him, and may even derive advantage 

 from those very errors. From the study of the Desmidiese, and from their 

 . being brought into comparison with animals, valuable notions upon the in- 

 timate structure of vegetables have already been derived." — Sulla Animalita 

 della Diatomee, p. 172. 



