Life History of Monads. By W. H. Ballinger ^ J, Drysdale. 1 87 
other. Indeed, from the fact of their being all in the same fluid, 
and developing in the same field at one time, it appeared perfectly- 
natural — if it had been permissible — to assume from the then 
known facts that the springing form was a younger condition of 
the biflagellate, and the calycine a higher development of the 
latter. So strongly did we at one time believe the facts to point 
in this direction, that when we had followed a calycine form to the 
state of encystment, to be presently described, we did not hesitate 
to express the conviction in our diary that in a few hours the field 
would be full of the young of the springing monad ! — a prophecy 
which the event completely falsified, administering by that means a 
salutary caution, and opening up one of the many pathways made 
known to us by our failures, and leading to the truth. Indeed, it 
became perfectly clear after continued work that we could never 
conclude that the contents of our continuously moist field, at any 
given time, were necessarily sprang from the most conspicuous 
forms predominant some little time before ; and therefore until the 
complete life cycle of any given group of forms is known, nothing 
can be certainly affirmed concerning them. 
It may be interesting to allude to the peculiar phenomena 
presented by the monads when they had been for some hours in 
our moist cell. We take an example when our maceration was 
most prolific in the variety of forms present ; some hours after the 
" dip " had been put into the chamber and under examination, the 
monads ranged themselves in zones; and these zones were per- 
sistent, however many days this drop might be preserved in 
unevaporated condition. The illustration is taken from our diaries 
in 1873; it is seen in Fig. 1, which is a portion of the field after 
it had remained under examination in the moist chamber four days. 
B C represents the margin of the cover-glass — the field being seen 
with a comparatively low power — d d is an outermost zone, in this 
instance, of the " springing monad " ; these were in intense activity, 
constantly changing places with a rapid spring, but always pre- 
serving the zone in its integrity. At a distance from this zone 
about equal to its own width came another, composed largely of 
the " biflagellate " form, and an immense number of the young of 
this, and probably of other forms also, intensely active, shown at 
e e ; and finally within this, a zone of what with comparatively low 
powers would be taken merely for bacteria, but which under the 
scrutiny of the highest powers proves itself to be composed by no 
means in the larger proportion of these, but to consist of still and 
active germ-like bodies, the development of which with care and 
persistence may be followed. This is drawn at//. Swimming 
abo.ut freely between and within the zones were stragglers from all 
of them, with many other forms in no way connected with them. 
This was, with variations merely as to which monad or group 
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