OF CILIATED INFUSORIA 235 



spherical and unchanging in outline, though vacuoles occasionally 

 appear in their substance. Growth continues up to a certain 

 point, and when it ceases, the previously diaphanous, limiting 

 membrane becomes converted into a more or less thick-walled 

 cyst. 



In their early stages these amoeboid corpuscles, destined to grow 

 into ciliate matrices, have a very close resemblance to the discrete 

 corpuscles, which I have previously spoken of as developing either 

 into Monads or Amoebae. They are to be distinguished, however, 

 by two peculiarities, {a) by the fact that the embryo matrices 

 almost invariably stain of an old-gold colour with Ehrlich's eosino- 

 phile fluid (in the proportion of three or four drops to the drachm 

 of distilled water) while the ordinary discrete corpuscles remain 

 unstained ; and (&) by the further peculiarity that they are found 

 not only smaller but also much larger than these latter corpuscles, 

 so that when aggregated the units may be seen to vary much in 

 size, instead of being nearly all of one size, as the discrete cor- 

 puscles are commonly found to be. 



These various peculiarities in regard to the amoeboid origin of 

 the matrices are illustrated in Fig. 49, in which A ( X 500) shows 

 many of the coming matrices in their very earliest stages, together 

 with a few of them larger and more developed, taken from a hay 

 infusion on the eighteenth day, in which myriads of them were 

 appearing and growing in the pellicle. B ( x 375) shows three of 

 these bodies unstained, each of them about 1/3000 inch in diameter, 

 from a hay infusion on the twenty- sixth day ; and another of about 

 the same size, but stained with eosinophile. C and D (x 200) show 

 a number of these amoeboid matrices of larger size, in the pellicle ; 

 and also some cysts of the kind to which they ultimately give 

 rise, taken from another hay infusion on the thirteenth day. 

 E ( X 37S), from a hay infusion on the eleventh day, shows two 

 of the amoeboid matrices just before, and two after, encystment — 

 one of the latter containing a revolving embryo Ciliate (as indicated 

 in the photograph by its homogeneous rather than granular appear- 

 ance). In F (X 250) an amoeboid matrix just about to encyst is 

 also shown, to the right of the thick-walled, knobby cyst, of 

 the kind which it will speedily form. Multitudes of others were 

 seen in all intermediate conditions. 



These secondaiy matrices, when mature, almost always develop 

 comparatively thick cysts, and the embryos within them sometimes 

 remain for many days or even weeks in a motionless condition. As 



