268 HETEROGENETIC ORIGIN 



was also first seen revolving, though rather more quickly, within 

 its egg-case. After the application of a weak solution of iodine 

 its movements became so rapid that it burst the egg-case, though 

 it was killed before it could completely issue therefrom. Indica- 

 tions of cilia are to be seen at its anterior extremity. These 

 speedily become much more distinct ; thus Fig. 66 shows a free 

 swimming specimen, which was killed with a weak solution of 

 iodine soon after emerging from the egg-case. It presents the 

 common appearance of these organisms as they escape : the body 

 being densely packed with brownish globules, which are appa- 

 rently modified representatives of the original vesicles so abun- 

 dantly present in the earHer stages of the transformation.' 

 Sometimes, however, such globules are scarce or almost hidden, 

 their place being taken by mere granules, and then the large elon- 

 gated nucleus is occasionally visible without the aid of reagents, as 

 in the small specimen shown in Fig. 69, A. 



Whether the organisms have the body densely packed with 

 brownish coloured globules on escaping from the egg-case, as in 

 Fig. 66, or with mere granules as in 69, A and D, I have found to 

 depend, in the main, upon the length of time they have been 

 revolving within the egg-cases previous to their escape. If the pots 

 are opened soon after their complete formation, the Ciliates are 

 found to be densely packed with globules ; but if they are not 

 opened for two or three days after the time in which they are 

 usually formed, the Ciliates are found still revolving within their 

 egg-cases, but containing only granules in their interior. It would 

 appear that, after the complete formation of the Ciliates, they go on 

 slowly revolving within the egg-cases, so that the globules are pro- 

 bably, in part, used up as food products during the two or three 

 days in which they are doing this work, while obtaining no food 

 from without. As a rule, it is not till the pots are opened that the 

 Ciliates, under the stimulus of hght (and especially the concentrated 

 light of the microscope lamp), begin to move more rapidly within 

 the egg-cases, and succeed in effecting their escape. Once free, 

 they dart away with the most rapid movements, associated often 

 with rotations of the body on its longitudinal axis. 



Occasionally, while still within the egg-case, the embryo Ciliate 

 divides into two, and one of the products of such a division is the 



• These more opaque globules of the developed organism often assume their 

 original vesicular appearance, when the specimen is mounted in a mixture of 

 glycerine and water. 



