568 
Proceedings of the Pioycd Society 
In 1881 Julin and E, van Beneden proposed the homology of the 
neural gland in the Tunicata with the vertebrate pituitary body. 
Professor Herdnian has suggested a modified theory — that the neural 
gland, its duct, and the dorsal tubercle (and therefore also the 
original pituitary body) were formed by the conjunction of a 
primitive renal organ and a sense organ. 
Some of Professor Herdmaii’s views have been subjected to con- 
siderable criticism by continental biologists, but it is universally 
acknowledged that his remarkable series of papers on the Tunicata 
are characterised by great ability, and the Council have accordingly 
adjudged to Professor Plerdman for these papers the Neill Medal. 
The following Communications were read : — 
1. On Efficiency of Clothing for maintaining Temperature. 
By Sir W. Thomson. 
2. On the Law of Inertia ; the Principle of Chronometry ; 
and the Principle of Absolute Clinural Best, and of 
Absolute Kotation. By Professor James Thomson, 
LL.D., D.Sc., C.K 
There is no distinction known to men among states of existence 
of a body which can give reason for any one state being regarded as 
a state of absolute rest in space, and any other being regarded as a 
state of uniform rectilinear motion. Men have no means of know- 
ing, nor • even of imagining, any one length rather than any other, 
as being the distance between the place occupied by the centre of a 
ball at present, and the place that was occupied by that centre at 
any past instant ; nor of knowing or imagining any one direction, 
rather than any other, as being tire direction of the straight line 
from the former place to the new place, if the ball is supposed to 
have been moving in space. The point of space that was occupied 
by the centre of the ball at any specified past moment is utterly lost 
to iis as soon as that moment is past, or as soon as the centre has 
moved out of that point, having loft no trace recognisable by us of 
its past place in the universe of space. 
There is then an essential difficulty as to our forming a distinct 
