ï. ikeda: a new astomatous ciliate 



nized a very thin but distinct layer, which is characterized by being strongly 

 refractive and by extending in an irregularly wavy way when viewed in 

 optical section. The wide space internal to this réfringent layer is occupied 

 by a clear fluid-like substance. 



The parasites were fixed, together with the host, with picro-acetic 

 acid and were in part sectioned and in part mounted in toio. The sections, 

 5ju thick, were stained with either iron-haematoxylin or Delafieli>'s 

 haematoxylin, with or without the use of eosin as a counter stain. Un- 

 fortunately it was found that the effects of fixing were not in all respects 

 satisfactory. In the larger specimens the superficial cytoplasmic layer and 

 the underlying réfringent layer have become in many places widely 

 separated from each other. It is not quite clear how such a disturbance as 

 this was brought about only in the larger specimens. Possibly it may be 

 due to the fixing reagent having caused contraction of the extensive refrin- 

 \* g ent layer. Fig. 2 represents a median 



longitudinal section of a large specimen 

 stained with Delafjeld's haematoxylin and 

 eosin. The large clear spaces (marked 

 with ■*) visible between the plasmic cortex 

 and the layer of darkly stained threads 

 representing the réfringent layer that we 

 have seen in the fresh state, are the arte- 

 facts just referred to. The same is evidently 

 also true of the similar spaces in the central 

 parts. One of the remarkable structural 

 peculiarities shown by the larger, and there- 

 fore probaby full-grown, individuals consists 

 in the fact that the cytoplasm is extra- 

 ordinarily sparse in quantity as compared with 

 the large size of the entire body. It merely 

 F,g- 2 - forms a thin layer covering the body, the 



A longitudinal section of a 



fully grown M. sagittae. x 370. greater part of the latter being taken up by 



