38 INTRODUCTION. 



into which the previous heads had been slit (thus realizing the 

 ancient fable of the Hydra), could even regenerate the whole 

 from a minute portion, so that when the body of one individual 

 was positively minced into fragments, each of these should grow 

 into a new and complete polype, could endure being turned 

 inside out, so that what \vas previously the external surface 

 should become the lining of the stomach, and vice versa , and 

 could sustain various other kinds of treatment not less strange 

 (such as the grafting of two individuals together, head to head, 

 or tail to tail, or the head of the one to the tail of another), not 

 only without any apparent injury, but with every indication, in 

 the vigor of its life, of being entirely free from suffering or 

 damage? (See Chap. XI). It was by our own countryman, Ellis, 

 that the discoveries of Trembley were first applied to the elucida- 

 tion of the real animal nature of the so-called Corallines ; J the 

 structure of which was so carefully investigated by him, that 

 subsequent observers added little to our knowledge of it, until a 

 comparatively recent period. 



The true animalcules were first systematically studied, in the 

 latter part of the last century, by Gleichen, a German micro- 

 scopist, who devised the ingenious plan of feeding them with 

 particles of coloring matter, so as to make apparent the form and 

 position of their digestive cavities ; and this study was after- 

 wards zealously pursued by the eminent Danish naturalist, Otho 

 Fred. Miiller, to the results of whose labors in this field but little 

 was added by others, until Professor Ehrenberg entered upon the 

 investigation with the advantage of greatly improved instruments. 

 It was at about the same period with Miiller, that Vaucher, a 

 Genevese botanist, systematically applied the Microscope to the 

 investigation of the lower forms of Vegetable life ; and made 

 many curious discoveries in regard both to their structure and 

 to the history of their lives. He was the first to notice the ex- 

 traordinary phenomenon of the spontaneous movement of the 

 Zoospores of the humbler aquatic plants, which is known to be the 

 means provided by nature for the dispersion of the race (Chaps. 

 VI, VH) ; but being possessed with the idea (common to all Natu- 

 ralists of that period and still very generally prevalent) that spon- 



rhi " 



taneous motion evinces Animal life, he interpreted the facts which 

 he observed, as indicating the existence of a class of beings which 

 are Plants at one phase of their lives, and animals at another, 

 a doctrine which has since been completely set aside by the ad- 

 vance of physiological knowledge. Notwithstanding this and 

 other errors of interpretation, however, the work of Vaucher on 

 the "Fresh-water Confervse" contains such a vast body of accu- 

 rate observation on the growth and reproduction of the Micro- 

 scopic Plants to the study of which he devoted himself, that it is 

 quite worthy to take rank with that of Trembley, as having laid 



1 The structures to which this term is now scientifir.ally restricted, are really vege- 

 table. 



