

1905.]  Ciliated Infusoria within the Eggs of a Rotifer. 387 
gatherings of eggs were made at intervals of six hours, and among such eggs 
as were subsequently taken from the pots I found that from 12 to 25 per 
cent. yielded Otostomata rather than Hydatine. 
When the pots have remained covered and undisturbed for 36 hours at 
a temperature of about 17° C., one of them may be opened, and some of the 
small masses of eggs from the bottom of the pot should be taken up with 
a tiny pipette and placed in a drop of water on a microscope slip. Before 
covering the specimens, a minute fragment of a cover-glass should be placed 
at each side of the drop of water, so as to protect the delicate eggs from 
undue pressure. 
On examination by a low power of the microscope it will be seen that 
there are many empty egg-cases, that within some eggs there are embryo 
Hydatine in different stages of development, while within the remaining 
eggs the contents will be wholly different, consisting of an aggregate of 
minute pellucid vesicles, each containing a few granules, together with a 
variable amount of granules interspersed among the vesicles, as in Plate 7, 
fig. 4. 
A newly laid egg is shown in fig. 1, while figs. 3 and 4 represent two 
intermediate stages between it and the condition represented in fig. 4. 
In fig. 5 we have six Hydatina eggs and an empty ege-case, shown under 
a lower power, all of which were taken from one of the pots after 36 hours. 
The three central eggs are in the vesicular stage of transformation into 
Ciliates, while the three others show Hydatine in different stages of develop- 
ment. 
If the cover should be again placed upon this pot with a view to the 
examination of other portions of its contents 24 or 36 hours later, and this 
examination is made, it will be found that no further advance has taken 
place, that the eges previously in the vesicular condition still remain in this 
stage, and are, in fact, no further developed than some of their fellows were 
when previously examined. 
I have found on many occasions that the opening of a pot at an early 
stage of the transformation—even for only four or five minutes—arrests the 
whole process of change. It was for this reason that I advised three separate 
pots to be charged, so that their contents might be examined at different 
periods. 
When, however, a second pot is opened two and a-half or three days after 
the eggs have been placed therein, and portions of its contents are examined 
in the same way, a larger proportion of empty egg-cases will be seen. 
There may be few or even no developing Rotifers still remaining within the 
eggs, and in other ege-cases, instead of the motionless vesicular contents 
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