200 
JOURNAL OF THE PLYMOUTH INSTITUTION. 
objective was made in this country. Science was not slow to avail 
herself of the great help thus offered her. and every year has added 
to the number of discoveries of vast importance which have been 
made in every department of Biology by means of this grand 
instrument. 
It may be in the recollection of some of my hearers that at the 
meeting of the British Association in this town, in 1877, the Eev. 
V. H. Dallinger read a paper before the Biological Section, " Ee- 
searches on the Life History of the Simplest Organisms." This 
was a communication of great interest, and the results obtained 
being the outcome of much patient labour and delicate manipula- 
tion, the author obtained well-deserved praise. This year he was 
asked to deliver one of the popular lectures at the Sheffield 
meeting, which he undertook to do, but unfortunately illness 
prevented him carrying out his intention. In the paper to which 
I have referred — " Eesearches on the Life History of the Simplest 
Organisms" — he summed up the results of four years' careful work, 
some details of which had before appeared in the Microscopical 
Journal, by Mr. Dallinger and Dr. Drysdale. The life histories of 
six monads had been worked out. These monads are at present 
subjects of doubt as to whether they should be cousidered as 
animals or plants. " They are minute, free or fixed, rounded or 
oval bodies, provided with one or more long cilia, and usually 
provided with a nucleus and contractile vacuole."* The motions of 
these bodies, whatever they may be, are of the most graceful kind, 
and this motion, it seems, depends upon the number of the flagella 
or cilia, which range from one to four. The investigations showed 
that the life histories of these forms were perfectly complete, and 
definite ; that when ordinary air was charged with given germs any 
nutritive fluid receiving those germs would produce monads, while 
if the air was kept perfectly pure, no monads appeared. Monads 
suddenly plunged into fluid of seventy degrees were destroyed, but 
if the fluid was gradually raised even up to 127 degrees, they not 
only lived but multiplied rapidly. The investigations were con- 
tinued, and the next paper was read before the Eoyal Society, 
being the "Life History of a Septic Organism." The delicacy of 
the experiments was remarkable, the main work being done with 
a thirty-fifth objective, but a fiftieth was also employed, and 
inasmuch as the organism never exceeded one four-thousandth of 
* Huxley. 
