THE MICROSCOPE. 33 
These are some of the advantages of the form I have to offer 
to the world, and which Mr. Bulloch has pirated in such unblushing 
fashion. 
A MICROSCOPICAL INCIDENT. 
BY DR. ALFRED C, STOKES, 
HE reader is probably familiar with that attractive little 
thizopod Acanthocystis chetophora, if not by observation at 
least through Dr. Leidy’s monograph on the class. Until the oc- 
currence of a certain event in which it took an interested if not an 
active part, I thought it as delicate as it is pretty, but I had occasion 
to change that opinion since the animal showed so much endurance 
in a struggle it was forced to make. 
Acanthocystis is not uncommon in shallow water and among 
aquatic plants, and, comparing a small thing with a large one, rather 
ignobly and inaccurately too, it may be likened to a living, vivid 
green, spherical pin-cushion thrust full of crystalline needles and 
pins, the heads of the latter not rounded but furcated, with widely 
diverging rays. This unjust comparison, of course, tells but half 
the story. The rhizopod is a soft mass of finely granular proto- 
plasm mingled with very many bright green particles, its surface 
profusely studded with silicious spines rising from minute basal 
discs, thus giving the animal a rather formidable appearance among 
its more plainly dressed neighbors. Through the interstices of its 
armor are protruded the thread-like pseudopodia, and enveloping 
the whole body is usually an external layer of protoplasm defined by 
small linear or bacteria-like bodies. The utility of this outer en- 
velope is known only to its possessor. 
Recently one of these spinous creatures appeared under my 
microscope. It seemed to be alive and well, but within it near the 
armored surface, was a _ semi-transparent moving something 
that was too active to have a right there. As the motions of 
this foreign body became more impulsive it turned completely over 
and showed itself to be one of the rotifers. In size it equalled not 
more than one-third the Acanthocystis’ diameter, but dwarfish stature 
was amply compensated by nimbleness. 
With a leap, prodigious for so small a creature, the rotifer dashed 
against the wall and hurled the rhizopod down the field, while 
