192 Transactions of the Boyal Microscojpical Society. 
fission, and the more carefully this process is studied, the more 
remarkable it appears ; for we have here not a uniform homogene- 
ous rod of sarcode like the bacterium which we can easily imagine 
by mere growth to elongate and divide by transverse fission, as it is 
said to do, but we have a creature of distinctly marked shape, a 
certain amount of structure and difi'erentiation of parts, of which 
each part appears to generate a counterpart of itself. How long 
this process may be going on we cannot exactly say, but the time 
taken in visible separation is from five to sixty minutes ; but several 
times one-half of a fission has been followed, and whatever internal 
processes may have been at work must have been completed in from 
twenty to thirty minutes, for after that time fission has again 
ensued. But in every case the division results in two individuals 
equal to each other in shape and apparent size ; a little less in bulk 
than the original monad, but in every sense as perfect. 
The process is as follows. An actively swimming form becomes 
soft and plastic ; the posterior end loses its sharpness, and be- 
comes blunt and rounded. At the same time a semi-amoeboid state 
ensues all over the sarcode, causing singular projections in every 
part of the body. In this state the nucleus-like body becomes very 
developed, and often is surrounded by what appears like something 
flowing from its substance. The " calycine " in this condition is 
drawn at Fig. 3. This may be repeated several times, after which 
a comparatively pear-shaped form is taken, the flagella being at the 
broad end : during the whole of this time the sarcode is in vivid 
internal motion — a kind of self-acting kneading process. At this 
time the root of the flagella is seen distinctly to split, dividing them 
into two separate pairs ; and at the same moment a motion is set up 
which pulls the divided pairs of flagella asunder, making the inter- 
val of sarcode to grow constantly greater between them. This is 
seen in Fig. 4, where a, h show the complete division of the thick 
quadruple base of the flagella, and the arrows show the direction in 
which each pair is pulled. At the same time the nucleus shows 
marked symptoms of constriction, as is shown at c. From this time 
there is a tendency to take a rounder form, while the separate pairs 
of flagella rapidly diverge, as shown in Fig. 5 ; the flagella still 
moving in the direction of the arrows, and the nucleus-like body 
still more completely divided. The opening between the two pairs 
of flagella now rapidly increases, and the mass of sarcode becomes 
bean-shaped, as in Fig. 6, the nuclear disk having completely divided 
into two ; at the same time an internal indication of constriction is 
given at a ; and very shortly the two pairs of flagella have reached 
a position exactly opposite each other ; the constriction has become 
very decided, as seen in a, Fig. 7, and the parts now evidently sepa- 
rating pull against each other, as seen by the arrows in the same 
ligure. From this time the constriction rapidly deepens, the two 
