OF CILIATED INFUSORIA 265 



of the pot should be taken up with a tiny pipette and placed in a 

 drop of water on a microscope shp. 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 Hydatinee 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. 



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 eggs which presumably were 

 previously in the vesicular condition still remain in this stage, 

 and are, in fact, no further developed than those of their fellows 

 which were 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 

 egg-cases, instead of the motionless vesicular contents previously 

 seen, a great Ciliate may be found slowly revolving, or else, under 

 the influence of the light, rupturing the egg-case, struggling out, 

 and swimming away with rapid movements, partly of rotation. 

 Some of the Infusoria, before they emerge, undergo segmentation 

 into two, four, or, rarely, even into eight smaller CiUates. 



As a control experiment, it will be well, at the time that the pots 

 are charged, to place two or three batches of the eggs with some 

 of the same water into a watch glass, which is left exposed to 

 light ; and at the expiration of three or four days, as well as at 

 later periods, to search among its contents for any of the same large 

 Ciliates (which, when moving, could be easily distinguished with 



