his
form--extending over four years--he had the advantage of the highest
quality of homogeneous lenses obtainable, ranging from one-tenth to
one-fiftieth of an inch, his chief reliance being placed upon a very
perfect one thirty-fifth of an inch; and from the continuous nature of
the observations as well as the circumstances under which they were
carried on, dry lenses had for the most part to be employed. Having in
his possession a maceration of cod-fish in a fluid obtained from boiled
rabbits, he found at the bottom of it, when in an almost exhausted
condition, a precipitate forming a slightly viscid mass, to which his
attention was particularly directed. It was seen to contain a vast number
of _Bacterium termo_, but on examination with a one-tenth inch objective
showed that it also contained a comparatively small number of intensely
active organisms--one being discovered in about eight or ten drops of the
sediment. These measured 1-10,000 of an inch in length by 1-19,500 of an
inch in breadth. The fluid had originally been kept at a temperature of
90 deg. to 95 deg. F., and it was noticed that, when placed upon a cold stage
under the microscope, the movements of the organisms became, gradually
slower, until at last they entirely ceased; the necessity, therefore,
arose for the use of a warm stage, and the very ingenious contrivance by
which a continuous and even temperature was maintained within the
one-tenth of a degree was exhibited. The greatest difficulty in the
matter was, however, experienced in obtaining specimens for observation,
in order to be able to trace them from their earliest to their latest
stage. The President then explained, by means of an admirable series of
illustrations projected upon a screen by the oxyhydrogen lantern, the
life history of the organism to which he had referred, exhibiting it
first as a translucent, elliptic, spindle-shaped body, with six long and
delicate flagella, the various positions in which the five specimens were
drawn giving a very good idea of its peculiar porpoiselike movements.

The various positions which it assumed in making an attack upon a portion
of decomposed matter were also shown, the movements quite fascinating the
observer by their rhythmical character. The supposed action of the
flagella in the production of the movements observed was explained,
distinct evidence being afforded of a remarkable spiral motion, at least
of those behind. The process of fission was