OF CILIATED INFUSORIA 239 



which are often much more, and rarely less, than i/iooo inch 

 in diameter, and are, from the first, small Ciliates. These are the 

 only bodies that can in any sense be regarded as " spores " among 

 the Ciliata, which have for years been the subject of numerous and 

 most elaborate investigations by skilled observers. Their only 

 known modes of increase hitherto have been by processes of 

 fission, occurring either when in their free state or when encysted ; 

 and, though much more rarely, by processes of gemmation. 



(4) But it has been found that the Ciliates which first appear in 

 our filtered organic infusions as nearly full-sized, free-swimming 

 organisms are always preceded in the pellicle by encysted matrices 

 from which they develop. These matrices could never, as such, 

 have passed through the filter ; and, even if they had done so, 

 looking to their size and weight, they would have accumulated 

 at the bottom of the vessel rather than at the surface of the fluid. 

 They could not have got into the pellicle at all unless they, or the 

 bodies from which they have been derived, had previously enjoyed 

 an active life. But, as I have said, the matrices appear in the 

 infusions before the Ciliates. 



(5) In the face of these facts we are driven, therefore, to the 

 conclusion that the primary matrices must be formed from the 

 pellicle itself. And that is what I have shown to be actually 

 the case. The early stages of these matrices have been demon- 

 strated to be mere aggregates of Bacteria, of a kind similar to those 

 existing in the pellicle around them. Each of these aggregates 

 becomes enclosed by a delicate bounding membrane, develops a 

 nucleus, and then becomes evolved into an active embryo Ciliate. 

 This embryo may be seen revolving within its cyst, previous to 

 rupturing it and moving away as a free-swimming organism.' 



This mode of origin of Ciliates from the pellicle is, moreover, 

 in exact accordance with what I have shown to be the mode of 

 origin of small Zoogloea masses in and from the pellicle, and also 

 with the discrete modes of origin of Monads and of Fungus-germs. 

 We are alike incapable of explaining either set of facts, and how- 

 ever indisposed biologists may be, at first, to believe that these 



' The cyst is colourless and very delicate, and there is no space between it 

 and the embryo. But after from four to six days of free life very many of these 

 Kolpodae become motionless, assume a spherical shape and secrete a cyst. 

 The body thus encysted speedily presents a totally different appearance from 

 that of the primary matrices, seeing that its cyst though smooth is thicker and 

 Of a pale brown tint, while a narrow space exists between it and the contained 

 organism — owing to its having undergone a slight diminution in bulk. 



