PLANTS, OR ANIMALS ? 7 



nomy of these microscopic beings, and at the various wonders 

 which they display. 



It may seem an odd way of beginning a volume on the curi- 

 osities of animal life to commence with an account qf objects 

 which belong to the vegetable kingdom ; but all things con- 

 sidered, the proceeding is by no means so Hibernian as may at 

 first sight appear. 



The truth is that, in dealing with these minute forms of life, 

 we are venturing on what has aptly been called the border 

 land of the organic world the frontier territory, so to speak, 

 which lies between the two great kingdoms of animated nature ; 

 and, as in many another case of disputed boundary, the inha- 

 bitants of the debatable region have sometimes been claimed for 

 the one side and sometimes for the other ; and in this case it 

 has so happened that many of them have occasionally been 

 claimed with equal vehemence by both sides at once. The 

 dispute as to what constitutes the essential difference between 

 plants and animals can hardly yet be said to have terminated ; 

 and though there is now a very general concurrence of opinion 

 that the distinction mainly consists, on the one hand, in the 

 dependence of the being for nutriment on organic substances 

 already formed, which in some way or other it takes into the 

 interior of its body, and, on the other hand, in the possession of 

 the power to obtain its nourishment by absorption from the in- 

 organic elements on its exterior ; yet this is a test which, in the 

 nature of the case, is exceedingly difficult of application to these 

 microscopic organisms. The power of spontaneous motion, Avhieli 

 was at one time relied upon as a distinguishing mark of animal life, 

 has long since lost its value in that respect, as it is now well 

 ascertained that not only the early immature forms, but the fully 

 developed individuals of many of the simplest aquatic plants arc 

 endowed with very active powers of locomotion, and, to all ap- 

 pearance, dance as merrily through the water as any of their 

 compeers of the animal series. It has been argued, again, that 

 the presence of what are known as contractile or pulsating 

 spaces in the interior of the body is a proof of animality, but here 

 also the progress of research has gone against the assumption, 

 these contractile spaces being now known to be common to lx>th 

 the animal and the vegetable kingdoms. Owiug to this appa- 

 rent animality of many of these humble plants, it is extremely 



