THE INVISIBLE WOELD. 153 



height to which it must be carried, of the time when this 

 must be done ; a will to commence and to go on, a will to 

 leave oflf, (for the ciliary current is entirely imder control) ; 

 a consciousness of the readiness of the peUet ; an accurate 

 estimate of the spot where it needs to be deposited ; (may I 

 not say also, a memory where the previous ones had been 

 laid, since the deposition does not go on in regular suc- 

 cession, but now and then, yet so as to keep the edge 

 tolerably uniform in height t) ; and a will to determine that 

 there it shall be put. But surely these are mental powera 

 Yet mind animating an atom so small that your eyes 

 strained to the utmost can only just discern the speck in 

 the most favourable circumstances, as when you hold the 

 glass which contains it between your eye and the light, so 

 that the ray shall illumine the tiny form while the back- 

 ground is dark behind it ! 



It is a startling thought that there exists a world of 

 animated beings densely peopling the elements around us, 

 of which our senses are altogether uncognisant. For 

 six thousand years generation after generation of Rotifera 

 and Entomostraca, of Infusoria and Protozoa have been 

 living and dying, under the very eyes and in the very 

 hands of man ; and, until this last century or so, he has 

 no more suspected their existence than if " the scene of 

 their sorrow " had been the ring of Saturn. Dr ^Mantell 

 wrote a pretty book, the secondary title of which was " A 

 Glimpse of the Invisible World." It was a book about the 

 Ani m a l cules, which are revealed only by the microscope ; 

 and though it gave little original information, and some of 



