ie i | 
1871.] 207 [Cope. | | 
CO. On the Transmission of Grade Influence. 
How force potential in nerve structure is inherited through the repro- 
ductive elements is a great mystery. The following considerations relate | i 
to it. | § 
1. Secre'ion is known to be conducted through the conversion of heat i | 
into growth force, probably through the intervention of nerve force. 1 ¥ 
2. In many secretions which possess strong chemical qualities, as gas- 
tric juice, bile, saliva, etc., the fluid is formed by a destruction of the 
cells representing the efforts of growth force, which is therefore no doubt 
converted into chemism or chemical force. 
8. In the spermatozodids, which are produced by a process of secre- [ 
tion, the cells are not destroyed, and thus growth force remains potential ; { 
they exhibit however lively motions, which may represent motive 
force derived from the nervous centre. 
4, While in contact with the yolk of the ovum, so long as vitality | 
lasts, the motion must be communicated to portions with which it is in | di 
contact, or converted into one of the forces from which it was derived 
(heat) or into another force (growth force). The growth force potential 
in the cell of the spermatozodid, on its destruction, becomes converted | 
into heat or other force. Thus may originate the growth force of the | | 
ovum, which, once commenced, is continued through the period of growth. | 
The process might be compared to the application of fire to a piece of 
wood. The foree conversion is communicated to other material than that 
first inflamed. The new fuel in the case of the embryo, is the pro- 
toplasm derived from the mother. 
V. ON INTELLIGENT SELECTION. 
As neither use nor effort can be ascribed to plants, and as we know 
that their life history is much more dependent on their surroundings, 
than is that of animals, we naturally look to the physical and chemical 
causes as having a prime influence in the origination of their type struc- 
tures. Without greater familiarity with the subject, I will not attempt ° 
to say how far the various degrees of growth force possessed by parent 
plants, located under the influence of meteoric and other surroundings, 
and preserved, destroyed or restricted by natural selection, may account 
for the characters of their successors of the present period. But other 
agencies similar to use, that is, automatic movements, may be also intro- 
duced as an element in the argument. ‘The movements of tendrils seek- i 
ing for support may be here considered, and as Dr. Asa Gray has pointed i 
out, have consequences similar to those of use in animals. When the ten- 
dril seizes a support, growth force is located at the point of contact, for 
the tendril increases considerably in thickness. 
Among animals of the lowest grade, movement must be quite similar 
to those of plants, or automatic from the start, and not even at the be- 
ginning under the influence of will. Evidence of will is, however, soon 
seen in the determinate movements of many of the Protozoa in the seiz- 
A. P. S—VOL. XII,—2G. 
