THE ROOT-PRIXCIPLES OF MIND. '51 



gives notice of the presence of prey, which is secured by the 

 slow bending of the tentacles. On the other hand, the sensi- 

 tive filaments of Dionoea are not viscid, and the capture of 

 insects can only be assured by their sensitiveness to a 

 momentary touch, followed by the rapid closure of the lobes." 

 So that in these two plants the power of discriminating 

 between these two kinds of stimuli has been developed to an 

 equally astonishing extent, but in opposite directions. 



But we find definite evidence of this power of discrimina- 

 tive selection even lower down in the scale of life than the 

 cellular plants ; we find it even among the protoplasmic 

 organisms. Thus, to quote an instructive case from Dr. Car- 

 penter : — 



" The Deep-Sea researches on which I have recently been 

 engaged have not ' exercised ' my mind on any topic so much 

 as on the following : — Certain minute particles of living jelly, 

 having no visible differentiation of organs .... build 

 up ' tests ' or casings of the most regular geometrical sym- 

 metry of form, and of the most artificial construction . . . 

 From the same sandy bottom, one species picks up the coarser 

 quartz-grains, cements them together with phosphate of iron 

 (?), which must be secreted from their own substance; and 

 thus constructs a flask-shaped ' test ' having a short neck and 

 a single large orifice. Another picks up the finer grains, and 

 puts them together with the same cement into perfectly 

 spherical ' tests ' of the most extraordinary finish, perforated 

 with numerous small tubes, disposed at pretty regular inter- 

 vals. Another selects the minutest sand-sprain and the 

 terminal points of sponge-spicules, and works these up 

 together — apparently with no cement at all, but by the 

 ' laying ' of the spicules — into perfect spheres, like homoeo- 

 pathic globules, each having a single fissured orifice." * 



Thus, co-extensive with the phenomena of excitability, 

 that is to say, with the phenomena of life, we find this func- 

 tion of s elective discriminatio n ; and, as I have said, it is this 

 function that I regard as tlie root-principle of Mind. I so 

 regard it because, if we consider all the faculties of mind, we 

 shall observe that the one feature which on their objective 

 side they present as common, is this power of discriminating 

 among stimuli, and responding only to those which, irrespec- 

 tive of relative mechanical intensity, are the stimuli to which 



* Contemporari/ Review, April, 1873. 



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