162 
“ Remarks on Molecular Activity as shown under the 
Microscope/’ by J. B. Dancer, F.R.A.S. 
The Author stated that, during the last 30 years, he had 
met with many microscopical observers who were not ac- 
quainted with the phenomenon, to which the name of mole- 
cular action has been given. This class of microscopists had 
confined their attention to objects requiring a very moderate 
amount of magnifying power, and generally to dry objects ; 
but when their investigations extended to minute objects 
immersed in fluid which required powers of 800 to 1500 
diameters, they were startled by the appearance of particles 
in active motion, not moving in a direct line, but vibrating 
as if attracted and then repelled by each other, some single, 
and others in clusters. 
Many instances have come under the author’s notice, in 
which these objects have been regarded by microscopists as 
animalculse. They have given rise to many very ingenious 
speculations, some of which are connected with spontaneous 
generation, these observers would have been saved much 
labour if they had been acquaintad with the experiments of 
the late Dr. Robert Brown on active molecules. 
The author does not imagine that the members of this 
section are wholly unacquainted with the experiments of the 
early microscopists on this subject, but in the absence of more 
important matter, he thinks a brief account of the early 
observations on these so called active molecules may interest 
them. 
The moving particles had been noticed by Leewenhock, 
Stephen Gray, Buffon, and others who supposed them to be 
animated matter. 
In the year 1827, the late Dr. Robert Brown, whilst 
engaged in the microscopical investigation of unimpregnated 
ovulum, noticed that the pollen of the clarckia pulehella was 
filled with particles, which appeared in active motion when 
immersed in water. These observations were followed by 
