OF CILIATED INFUSORIA 245 



which they were converted into flagellate Monads or Peranemata 

 have been already described (pp. 221-224) I but the question of their 

 origin was deferred. All that was said on the subject of the origin 

 of these spinous cysts was this : " I will only say that I have found 

 many thousands of them in association with a gathering of 

 Euglen^ ; and though I have seen many specimens of Stylonychiae 

 come out of them I have never seen a single one of them formed 

 by the encystment of such a Ciliate. They appear rather to have 

 been derived from much smaller matrices (found in association 

 with the more developed specimens) which gradually increased in 

 size and formed a thicker envelope, upon which the spinous pro- 

 cesses were finally developed. The mature specimens varied a 

 good deal in actual size." 



Such bodies as are to be seen in Fig. 52, A ( x 80), when they 

 have become slightly increased in size and show indications of a 

 nucleus, are represented, under a higher power, in B (x 250). 

 In C (x 250) two of these bodies are shown which have still 

 further increased in size, and the one on the right may be seen to 

 have begun to develop spines from the outer surface of its cyst. 

 Such spines, fully developed, are shown in D ( x 250), in which the 

 surface of one of these cysts has been focussed. E ( x 250) repre- 

 sents another of these bodies whose contained embryo had just 

 begun slowly to revolve within its cyst. When I proceeded to 

 photograph it no movements were appreciable, but these must 

 have been stimulated under the strong light from the lamp, the 

 result being the homogeneous appearance shown in the photo- 

 graph. The organism that has many times been seen emerging 

 from such a cyst, after a series of violent movements, has been 

 an embryo Stylonychia of almost full size. 



In other cases, the transformation into Ciliates of Euglenas that 

 come to rest on the surface of the fluid, and within cysts so thin as 

 to be scarcely appreciable, has been seen taking place much more 

 rapidly. I have traced all the stages in the formation of Nassulas 

 in this way; and will now describe and illustrate the mode in which 

 the transformation has been effected. 



Towards the end of November, 1901, after two days of sUght 

 frost, I procured from a ditch some damp mud on which there was 

 a coating of Euglenas. A portion of this was placed in a small 

 vase, which was then filled with water. The vase was left on the 

 end of the mantelpiece nearest the window in my study, covered 



