OF CILIATED. INFUSORIA 261 



kMk 



has the division been further advanced than it is represented as 

 being in these specimens. ' 



I am disposed to think that these Ciliates would develop into 

 Glaucomas, in vsrhich the mouth is very small, and often rather 

 difficult of detection. Their general shape and the very large size 

 of the nucleus is in accord with this supposition. Still, although 

 the nucleus in a Glaucoma is often very large and spherical, in 

 these embryo Ciliates it is far greater in proportion to the size of 

 the body than in any other Ciliates I have ever seen. 



It is perfectly clear, however, that the hundreds of Ciliates to be 

 found in the fly are extremely delicate embryos, as shown by their 

 texture and ready disintegration,^ and also by the change that 

 takes place in them and in the development of their cilia in the 

 course of twenty-four hours. That such large and frail embryos 

 could in any way penetrate the body of the fly from without (even 

 if the stage with languid movements and short weak cilia were their 

 first stage) would have to be regarded as almost impossible. But, 

 as we have seen, in their first stage they are really motionless bodies 

 contained within hyaline cysts, and there is no possible source for 

 such bodies, in such numbers, except from the immature ova, to 

 which they are closely allied in structure. 



This resemblance was seen by an examination of the loose 

 immature ova within the abdominal cavity, as well as of those that 

 were observed withii^ portions of the ovaries which had been ex- 

 truded from the abdomen of other flies. And in one of these flies, 

 where glycerine had been allowed to run in under the cover-glass, 

 so as gradually to replace the distilled water, I found six days 

 later, that the nuclei of the immature ova and also those of the 

 Ciliates had assumed a pale bluish tint — so that the nuclei in 

 each case presented an altogether similar appearance. 



The normal development of eggs seems to take place very 

 rapidly in these Psychodae, judging from what I have seen in one 

 of them. A living specimen of P. phalanoides was found containing 



' One of the flies which had been ascertained to contain hundreds of these 

 Ciliates, was left in the egg-emulsion for twenty-four hours, in the expectation 

 that the abdomen would be ruptured by its swarming brood and the Ciliates 

 liberated. But this did not happen, and on examination I found the whole body 

 of the fly densely packed with motionless and dead Ciliates. 



" In one case all of the Ciliates which had been left in water under a cover- 

 glass were found to be dead in four hours ; and on another occasion others, 

 under similar conditions in a damp chamber, were found after ten hours not only 

 dead but almost completely disintegrated. 



