238 HETEROGENETIC ORIGIN 



Some General Considerations Concerning the Origin of Ciliates in 

 Organic Infusions. 



In reference to the origin of Ciliates in filtered organic infusions 

 there are five sets of facts of cardinal importance which must 

 never be lost sight of. They are as follows : — 



(i) It has been found that the different infusions are associated 

 each with its own particular kind of Ciliate — that is, where such 

 organisms appear, for it must clearly be understood that they do 

 not show themselves in filtered organic infusions with anything 

 like the regularity that characterises the appearance of Bacteria, 

 or even of Monads. 



(3) Then, although the infusions after their preparation had 

 been passed through very fine filtering papers, the Ciliates which 

 first appeared therein in swarms (somewhere between the fourth and 

 the eighth days) were, when they first appeared as free-swimming 

 organisms, already of nearly full size — that is, even the smallest 

 of them (in the infusion of Galium verum) had seven or eight times 

 the diameter of the largest particle capable of passing through 

 such filtering papers ; while the larger specimens (found in hay 

 infusions) had at least twenty times the diameter of such particles. 

 It is well known that Swedish filtering papers will not exclude 

 particles of barium sulphate, and these, as I have found, have an 

 average diameter of 1/15,000 inch. 



(3) Ciliates are not known to be reproduced by any very minute 

 particles having the nature of spores or germs. Lankester says ' : 

 " Of the formation of ' spores ' in this group we are at present 

 ignorant, in spite of all that has been written on this subject." 

 Similarly Saville Kent writes = : " Among the higher orders of the 

 Class Infusoria sporular reproduction is comparatively rare, being 

 as yet almost unknown among the groups of the Tentaculifera, 

 while in that of the Ciliata a few stray instances only can be 

 cited." The "stray instances" spoken of by Saville Kent as 

 occurring among the Ciliata are, however, quite unworthy 

 of being considered as instances of spore-formation, seeing that 

 what he refers to, as instances of such a process, is the fission 

 of certain encysted Kolpodas, Otostomata, and one or two other 

 forms, into two, four, or eight segments — that is, into masses 



' Introduction to translation of Gegenbauer's " Comparative Anatomy," 1878 

 p. ix. 

 " " Manual of the Infusoria," 1881, vol. i., p. 89. 



