OF CILIATED INFUSORIA 271 



that he refused even to look at the specimens or photographs, 

 close at hand, in illustration of this remarkable transformation. 



Yet one may almost see the eggs laid by the Rotifers, busy in 

 their midst : for the eggs are large enough to be detected with the 

 naked eye, and can be most easily recognised with the aid of a 

 pocket-lens. When they have accumulated sufficiently at the side 

 of the vessel, masses of 20 to 30 or more may be taken up with a 

 knife, and transferred to a drop of water on a microscope slip. 

 We may then see that the little white spheres are all Hydatina 

 eggs, either newly laid or in different stages of development, and 

 that there are no Ciliates among them either free or encysted ; we 

 may place these masses of eggs in the pots, as I have directed, and 

 in three or four days we may open the pots, and often find in each 

 batch of eggs, if they had been freshly laid when collected, from 

 3 to 10 of the great Ciliates revolving within as many of the egg- 

 cases. And if we open the pots earlier, we may see the inter- 

 mediate stages in the transformation, as they are shown by my 

 photographs. 



It seems difficult, even allowing for a large amount of natural 

 incredulity at first experienced, to put more than one interpreta- 

 tion upon such facts. The unbiassed exercise of reason upon the 

 evidence adduced ought to make it clear. 



I have, however, other proofs which, added to what I have 

 already set forth, should suffice to bring conviction even to the 

 most sceptical. To one of these further proofs I will now direct 

 the reader's attention. 



During the last three or four years I have often observed that 

 when Hydatinse have been kept indoors for ten or more days, they 

 lay eggs very much darker in colour than usual — so that they have 

 an almost black appearance, owing to some slight alteration in 

 the nature of the granules entering into their formation. About 

 the same time ' resting eggs ' begin to appear, and also male 

 Hydatinas. 



I am aware that some authorities regard it as settled that the 

 Hydatina 'resting eggs,' are eggs which have been laid by 

 fecundated females. Although I am not prepared to traverse this 

 view, my experience leads me to think that ' resting eggs ' are 

 often found in abundance before male Hydatinas make their 

 appearance ; and I am inclined to think that the formation of 

 such eggs is intimately related to that change in the con- 

 stitution of the egg to which I have just referred as occurring 



