168 
Proceedings of the Royal Society 
both Latin and English have strong peculiarities distinguishing 
them from other languages, which help to conceal cognate words 
from each other, and which must be mastered before the double 
disguise can be seen through. 
He exemplified these views by detailed instances, and concluded 
by urging that all nations of the Aryan race ought to be regarded 
as susceptible of the highest culture, and that the good hopes 
might be entertained of their being all raised to as elevated a state 
of Christian civilisation as the best of them had attained. 
2. On the Genetic Succession of Zooids in the Hydroida. 
By Professor Allman. 
In this communication an attempt was made to express by 
means of formulae the various modifications presented by the life 
series of the Hydroida. It was also shown that there existed 
among the Hydroida both centripetal and centrifugal forms of 
development. These were compared with one another, and numer- 
ous analogies between the hydroid gonosome and the inflorescence 
of plants were demonstrated. 
3. On Green’s and other Allied Theorems. By Prof. Tait. 
(. Abstract .) 
In this paper an attempt is made to supply, at least in part, what 
the author has long felt as a want in the beautiful system of 
quaternions, so far as it has yet been developed. To apply it to 
general inquiries connected with electricity, fluid motion, &c., we 
require to have means of comparing quaternion-integrals taken 
over a closed surface with others extended through the enclosed 
space — and of comparing integrals taken over a non-closed surface 
with others extended round its boundary. The author recently 
found that he had already, in the Quarterly Math. Journal , and in 
the Proc. R. S. H., furnished the means of attacking the problem. 
By very simple considerations it is established that 
fff&V<rds = ff S. crUv ds, 
