260 THE AMERICAN NATURALIST. [VoL. XXXIV. 
these aggregations, he says, are due to “true chemotropism." 
In that portion of the work which deals with the way in which 
these aggregations are formed and with the part played by the 
organism, it seems to me that Garrey neglects certain facts 
that are absolutely fatal to the view of these matters which he 
puts forth. He did not determine the mechanism of the reac- 
tions of Chilomonas, — the exact way in which the organism 
moves when stimulated, — and this seems to me the first requi- 
site for an understanding of how the reactions are brought 
about. Garrey’s point of departure is his definition of tropism 
(which he says is the same as zaxis). 
Taking heliotropism as a type, he says: “ In heliotropism the 
organism is so oriented that its axis or plane of symmetry coin- 
cides with the direction of the rays, and symmetrical points on 
the surface of the body are struck by the light rays at the same 
angle." He then quotes with approval, for the case of chemo- 
tropism, Professor Loeb's generalization: * The essence of 
chemotropic orientation would then consist in the animals plac- 
ing themselves in such a position that symmetrical points on 
the surface of the body are cut by the diffusion lines at the 
same angle." The movement of Chilomonas into drops of 
organic acid, Garrey says, is “true chemotropism," and he 
states that the organisms move toward the center of diffusion 
“as if orienting themselves to radially disposed lines ; lines 
which may represent the paths of diffusing molecules or ions." 
From this one might infer that Chilomonas actually does so 
orient itself *that symmetrical points on the surface of the 
body are cut by the diffusion lines at the same angle," and 
then swims forward in this position, as required by the general- 
ization; Garrey says nothing to the contrary. Yet the animal 
does nothing of the sort. The very elementary fact seems to 
have escaped Garrey that Chilomonas, as is well known, is 
unsymmetrical, so that it is impossible for it to orient itself in 
this manner ; there ave no such symmetrical points to be thus 
cut. (In Chilomonas the so-called “upper” or larger lip lies at 
the dorso-dextral angle of the anterior end, as will be seen by 
consulting Fig. 9 ? of Pl. XLV of Bütschli's Protozoa, so that 
the animal is unsymmetrical both dorso-ventrally and dextro- 
= 
