INTRODUCTION. 25 



Mr. Dalrymple believes that orifices exist which are closed 

 by internal membranes. 



Ehrenberg, on the contrary, describes not merely open 

 orifices, but protruding organs or feet immediately behind 

 them, and thus affords an example of his want of caution 

 when he gives the rein to his poetic fancy ; for in this in- 

 stance at least he is clearly in error. Mr. Dalrymple, whose 

 remarks on the Closteria are the undoubted result of careful 

 examination, carried on with the desire of recording actual 

 facts rather than of supporting a theory, denies the exist- 

 ence of any papillae or proboscides at this part, and also the 

 supposition of Ehrenberg, that the moving molecules seen 

 near the extremities constitute the basis of such papillae. 

 This admission is the more valuable as coming from a person 

 who is not only an accurate observer but a believer in their 

 animal nature. Professor Bailey also informs us that he has 

 failed to detect them. 



In most of the Closteria there is at each extremity of the 

 endochrome a distinct globule containing moving granules. 

 Ehrenberg seems to have mistaken these for organs of mo- 

 tion. In Closterium rostratum and C setaceum these granules 

 are situated at a distance from the extremities, and, as they 

 are apparently not contained within a globule, move more 

 freely and afford better opportunities for observing them than 

 those in the other species do. In one instance I saw them 

 continue to move after escaping from the frond. Did the 

 Closteria possess mouths we should expect to find them in 

 every species ; but Penium interruptum, in which there are 

 conspicuous terminal globules and moving granules, has de- 

 cidedly nothing of the kind ; and as its end view is circular 

 and rather turgid no more desirable plant could be selected 

 for examination. If mouths are present they ought to be 

 visible in this and the allied species, but not a single punc- 

 tum can be detected in the end view of the empty frond. 



I have now passed in review the four points advanced by 

 Ehrenberg in support of the animal nature of the Desmidieae, 

 and I submit that I have shown that from them no evidence 



