THE FUNDAMENTAL ORGANIZATION 51 



Endosonies may consist entirely of chromatin as appears to be 

 the case in nuclei of some Microsporidia (Glugea and Thclohania), 

 or some flagellates (Prowazekia, Belar, 1920, etc.). Or they may 

 be composed of chromatin and plastin in various combinations. 

 Thus in Actinosphaerium eichhornii in some stages of nuclear activ- 

 ity, the chromatin component is in the form of an incomplete ring 

 which partially encloses the plastin portion (Fig. 23, C). In other 

 cases the plastin is entirely surrounded by a cortex of chromatin 

 which may be dense and compact as in the case of many types of 

 rhizopods and Sporozoa or loosely aggregated as in nuclei of End- 

 amoeba intestinalis (Fig. 24). The distributed granules of deeply 

 staining material which represent the substitute for a nucleus in 

 Dileptus gigas are similarly composed 

 of a plastin core and a chromatin cortex, / X 



the former increasing enormously after / - '^. ; « ^ 



treatment of the animal with certain /• -'.'';;" I * ' 1 



kinds of food such as beef broth. Here | « v ; , '■■ 



the term endosome is scarcely applicable " ^ ;-;| 



since the bodies in question are not in- {'% ',-.* \ ;j M " :, '■". ' 



side a nuclear membrane, but they appear ( ^Nfe • 'c ■*' 



to be morphologically equivalent to these 

 intranuclear structures. After treatment 

 with beef broth the body of Dileptus is 

 enormously distended due to the swelling x t v %,'<& 



of these cytoendosomes (Fig. 25). \'% '*^-^^ 



The centrally placed intranuclear body ^4§ . 



is generally described under the name 

 karyosome, a term which has been so r Jj G \f:~ E ' ldamoch ^ intes - 



. *. ' . , , „ ,, -r, hnahs; (e) endosome; (c) cor- 



widely used by students or the rrotozoa tex of chromatin. 

 and for so many obviously different 



structures that it is practically synonymous with endosome or 

 Binnenkorper. Thus Minchin describes it as a combination of chro- 

 matin and plastin; Doflein defines a karyosome as a centrally placed, 

 sharply outlined and constant constituent of the nucleus, which may 

 contain no chromatin or may be a combination of other substances 

 with chromatin and which divides during nuclear division, to form 

 two corresponding daughter structures. Hartmann's (1911) defini- 

 tion is more limited, a karyosome in his use of the term being an 

 endosome (Binnenkorper) containing a centriole. Belar (1921) finds 

 a "karyosome" in Chlamydophrys minor which breaks up and dis- 

 appears, forming neither chromatin nor kinetic elements. If we 

 attempt to combine these different views into a common definition 

 we find that a karyosome may be an intranuclear body which may 

 consist of plastin alone; or kinetic elements alone; or chromatin 

 together with plastin; or a combination of chromatin with kinetic 

 elements; or a combination of chromatin, plastin and kinetic ele- 





, 



