OF CILIATED INFUSORIA 233 



left represents one of the earliest stages of individualisation from 

 the pelUcle ; while three, rather more advanced specimens, are 

 situated close together to the right. The dark bodies obscuring 

 them are, as I have said, brown Fungus-germs out of focus, but in 

 each of these specimens nuclei in process of formation are to be 

 seen. Another of these bodies, more enlarged, from the same speci- 

 men, is shown in D (x 500), in which development has advanced 

 rather further — the nucleus being now very distinct, and having 

 taken up more of the very dilute stain than the body of the matrix, 

 and this again rather more than the surrounding pellicle. The 

 similarity in composition between the substance of the matrix 

 and that of the pellicle around it is well seen here, as in the other 

 specimens : and actual examination under the microscope 

 showed that the matrix had the same composition all through 

 its substance. 



The only Ciliates I have ever seen in the numerous hay or grass in- 

 fusions, made in the manner already described, have been Kolpodas, 

 either large or small, in association with matrices, similarly varying 

 in size. These matrices^ as I have said, appear in filtered infusions 

 before the free-swimming Ciliates. They appear in large numbers, 

 in the course of a few days, in the substance of the pellicle. But 

 in a few cases in which, in some early experiments, I added a small 

 quantity of unboiled tap- water after the infusion had been filtered, 

 another kind of Ciliate appeared in the infusions and rapidly multi- 

 plied therein.' In each case the Ciliates that appeared under 

 these circumstances were of the same kind. They were Chilodons, 

 though I have never seen the least evidence pointing to the origin 

 of these Chilodons in the hay pellicles. No matrices of such Cili- 

 ates have ever been found in the pellicles when they have been 

 present; nor have any of the Chilodons been seen in these in- 

 fusions in a state of encystment. I have not the least doubt that 

 the infusions were inoculated with the Chilodons when they were 

 diluted with the unboiled tap-water. 



It is the more notable, therefore, that the other hay infusions 

 with which I have worked, though prepared with the same kind of 

 tap-water and at temperatures under 100° F., should never have 

 shown one of these Chilodons. It seems difficult to explain such a 

 fact except on the supposition that the process of filtration adopted 



' If water is added for any purpose to the infusion after it has been filtered, 

 the addition ought always to be of water that has been recently boiled, or else 

 of water filtered as the infusion had been. 



