OF CILIATED INFUSORIA 241 



that I mean to convey thereby is that the CiUates in these cases 

 take origin from very minute corpuscles which are, at one stage of 

 their existence, almost indistinguishable from the discrete cor- 

 puscles that develop into Monads or Amoebas ; and that these 

 corpuscles go on increasing in bulk, always having very much 

 the appearance of small Amcebs in a resting stage, till they attain 

 varying sizes, ranging from about 1/2000 inch to 1/800 inch. 

 They then cease growing, develop more or less thick cysts, and 

 become converted into embryo Ciliates, which, after a time, may 

 be seen revolving within their temporary prisons. 



These amcsboid corpuscles, as I have said, stain of an old-gold 

 colour with a dilute eosinophile fluid, while the ordinary discrete 

 corpuscles that develop into Monads or Amoebae exhibit no such 

 reaction. Then again, these latter corpuscles are formed from the 

 pellicle of about the same size as the Monads and Amoebas to 

 which they give rise ; they do not grow in bulk, they only 

 develop. But the corpuscles that ultimately develop into Ciliates 

 begin as very minute bodies, which I have been able to trace by 

 the aid of stains down to 1/5000 inch in diameter ; and they grow 

 enormously, till they attain, previous to encystment, such sizes 

 as I have above indicated. 



The two modes of origin of Ciliates agree in this important 

 respect, that in each case the Ciliates are actually formed as such 

 within cysts ; and that in each case, also, the free-swimming 

 organisms emerge from the cysts approximately of full size. 



As to the actual source or origin of these minute particles which 

 appear after many days in the midst of the pellicle or of its out- 

 growths, and go on increasing in size till they become encysted 

 masses, each of which gives origin to a Ciliate, nothing definite 

 can at present be said. It may be surmised by some that they are 

 germs or minute spores derived from some previous Ciliates. But 

 against such a supposition various weighty considerations may be 

 urged. 



In the first place, as we have seen, no such germs or spores are 

 known, so that the supposition would be opposed to all existing 

 knowledge. 



Then, there is the fact that these bodies only show themselves 

 after ten or fifteen days ; and even then only when we have to do 

 with infusions four or five inches in depth, or so strong as to 

 be capable of forming thick pellicles from whose under-surface 

 numerous villous outgrowths project. In such zoogloeal out- 



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