29 
laws, which show that in the degeneracy of types, as well as in the 
old age of individuals, there is a decrease and a final disuse of char- 
acteristics which have been introduced during the rise of the group. 
The history of this characteristic follows the same law, and is pre- 
cisely in accordance with the history of other parts of the animal, 
and° precisely parallel with those which no one can deny to be 
hereditary. It will be very difficult for those who take the view that 
acquired characteristics cannot be inherited, to prove that this is 
not an acquired characteristic or that it is not inherited. It seems 
to me, as far as can be shown, without, of course, the direct demon- 
stration of experiment, that it is an acquired characteristic of 
purely mechanical origin which becomes inherited in the carboni- 
ferous. 
A Memeer: I should like to know what is the natural size of 
these shells. 
Pror. Hyatr: They are of all sizes. The largest of those 
described perhaps are three inches in diameter, others when full 
grown being much larger. ‘They are all of good size for obser- 
vation. 
Prof. Hubert A. Newton, of New Haven, Conn., represent- 
ing the Royal Society of Edinburgh, next addressed the Soci- 
ety, as follows: 
I have to apologize somewhat in that I came to the rooms not 
expecting to speak to you. I have, however, one point which I 
think will interest the members of this Society if they will give me 
a few minutes to develop it, and that is, the force which acts on the 
small bodies sent off from comets and which form our shooting stars. 
There are in the comets so many questions that we cannot answer, 
so many curious and wonderful phenomena that are unexplained, 
that I am sure you will accept any explanation of any of them that 
seems plausible, as a matter of interest. From a comet there is con- 
tinually driven off matter forming the tail, a light substance, and as- 
tronomers are agreed that the force that acts on the matter which 
forms the tail is a repulsive force from the sun acting inversely as the 
square of the distance, the force of the repulsion being greater than 
that of attraction. 
Not only is this true, but different parts of that tail are acted 
upon by repulsive forces of different powers; otherwise the tail 
