﻿88 P'roceedings of the Royal Physical Society. ^ 



somes appears to vary ; they may stand separately (Fig. 6), 

 or be bound together by what appears to be a nuclear 

 membrane. I am not quite clear as to whether this appear- 

 ance is really always due to the presence of a membrane, or 

 whether it may not be explained by the chromosomes 

 becoming confluent at their outer edges. In some cases this 

 appears to be the more probable explanation, as the connecting 

 band may sometimes be of very considerable thickness. At 

 anyrate, it is highly doubtful if this " membrane " can be 

 considered homologous with that found in the nuclei of the 

 Metazoa. This doubt is brought out very clearly, as will be 

 seen later, by its behaviour during division. 



Another variation in nuclear appearance is connected (Figs. 

 4, 11, 13) with the karyosome. This structure may be a small 

 and apparently simple granule, and may even, in some speci- 

 mens, be completely invisible; in others it takes the form of an 

 easily recognisable ring, which may or may not show several 

 thickenings. This ring-shaped karyosome is a very frequent 

 appearance, especially in the early Herpetomonas condition 

 (Fig. 11). At times there is a condensation of a blue 

 staining material, probably plastin, to be seen in the region of 

 the karyosome, this blue mass frequently bearing chromatic 

 particles (Figs. 8, 15-19). The chromosomes, which may 

 exceed the ordinary number, are usually joined by rays to the 

 enlarged karyosome. Very often the space (Fig. 16) between 

 the karyosome and the ring of chromosomes stains a pale pink 

 with the Eomanowsky stains. In this condition the nucleus 

 bears a resemblance to the nucleus of 2\ raim and to that 

 of many free-living flagellates. 



I wish here to remark that the word karyosome is used 

 under protest; this term is used in Cytological literature 

 to designate two different orders of structures. Strictly 

 speaking, a karyosome is a simple condensation of nuclear, or, 

 better, chromatic material; it is, in fact, a chromatic nucleolus. 

 In Protozoan literature it is applied impartially to a number 

 of doubtfully homologous structures, most of which are of a 

 complex nature, and not justly comparable to a metazoan 

 karyosome at all. 



The kinetonucleus, which is usually fairly large in size, is 



