OF CILIATED INFUSORIA 273 



been placed in the experimental pot : and as soon as their develop- 

 ment is completed they commonly make their way out — not waiting 

 for the stimulus of the light as is commonly the case with the 

 newly-developed Otostomas. 



These observations are surely very conclusive. Directly the 

 eggs vary from their usual condition, and become filled with black 

 granules, we find a concomitant variation in the Cihates issuing 

 therefrom — which is, of course, only to be expected if the Ciliate 

 is formed from the substance of the egg. 



But even this does not exhaust the evidence telling in favour of 

 the reality of this transformation of the whole substance of the 

 newly-laid Hydatina egg, when placed under certain abnormal 

 conditions, into a great Ciliate belonging to the genus Otostoma. 

 There is the additional fact that I have seen eggs, in the inter- 

 mediate or vesicular stage of this transformation, within the body 

 of a dead Hydatina ; and the further fact that I have seen a 

 fully-developed active Otostoma within the dead body of 

 another Hydatina. These observations have been made under 

 circumstances which I will now detail. 



When one of the experimental pots was opened at the end of 

 the second day in order to obtain specimens of the eggs in the 

 intermediate vesicular stage of the transformation, after having 

 taken out all the batches of Hydatina eggs that were visible at the 

 bottom of the pot, I noticed about a dozen separate bodies just the 

 size of HydatincB. These were taken up with a small pipette, and 

 on examination I found that they were really dead Hydatinae, in 

 difEerent stages of decay, but that nearly all of them contained two 

 or three eggs each, in different developmental conditions, though 

 all were about equal in size — a condition of things never to be seen 

 in living Hydatinae. In one, for instance, there were the three 

 eggs that are shown in Fig. 71, A (x 150). The upper one is a 

 black granule egg apparently in a mature condition ; another may 

 be in an early stage of normal development ; while the light egg 

 contained a moving and nearly fully-developed Hydatina. 



The contents of another of these dead Rotifers is shown in 

 B (x 200). Here also there were three eggs ; the substance of one 

 of them had almost disappeared, but the other two undoubtedly 

 represented different stages in the transformation of the eggs into 

 Otostomas. In the one in which the changes were most advanced, 

 the vesicular condition was most distinct. This is a condition 



18 



