16 Comparative Physiology and Psychology. (january, 
lar fibers, being placed, through the motion of elongation, in a 
state of inertia, enabling the contraction of the longitudinal with 
consequent adjustment of the circular fiber molecules, so they 
can act to advantage. The repetition of these two opposed mo- 
tions through the epidermal confinement of the skin, rendering 
them about the only ones that could be made, initiated by the 
-attractive affinities of the protoplasm, finally developed the con- 
tractile tissue. The ventral location of the nervous system in the 
Errantia and others is due to development through use of that 
region differentiating locomotor areas from the epidermis, and in 
Insecta it is the persistence of the phylogenetic origin. In the 
worm stage the external tactile becomes fully developed through 
the heterogeneity of molar vibrations to which it is subjected. 
One method of locomotion being possible, another is also pos- 
sible, differences or variations in one or the other, such as could 
be caused by mechanical means, could result in a sinuous move- 
ment arising from want of rigidity in the worm length. A com- 
plex of causes, simultaneous and successive, operate to change 
the usual mode of locomotion and introduce so-called compound 
reflexes. 
The formed tissue, of which Beale speaks, is often excremen- 
titious, and has, through being useful, been retained by the cells. 
The sandy covering of the rhizopod, Astrodiscus arenaceus, may 
have been “ selected” by agglutination of the envelope with the . 
particies, or the shell of a mollusk may form through excretory 
processes or a covering may be acquired by squatter right as 
with the hermit crab. It matters little to the animal. The fight- 
ing cock will use the steel gaffs with as much gusto as though 
they had grown from his legs, nor is the cell a particle more par- 
ticular. If it find in its environment matter with peculiar prop- 
erties it will, through “ selection,” eat what it can and excrete the 
rest. If the excreted material have enough affinity for the cell 
to remain in its vicinity, and a life process is subserved by that 
` fact, things chemical and mechanical in nature will conspire to 
associate the material with the cell. I regard nerve granules, 
such as are found arranging themselves or being arranged into 
first plexuses of fibers and then definite tracts, as having arisen 
accidentally. As the rhizopod could not have acquired his over- 
coat where there was no sand, the ancestral worm which picked 
up a nervous system could not have done so in the absence of 
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