254 THE PROTOZOA 



and other marine Rhizopoda (Fig. 134). Here the result of nuclear 

 activity is the formation of a nuclear membrane and a nuclear reticu- 

 lum, the meshes of which are rilled with karyolymph apparently de- 

 rived from the cytoplasm. Many of the stages which Schaudinn 

 described had already been observed in various Sarcodina by Hertwig, 

 F. E. Schultze, Biitschli, Gruber, Rhumbler, Hofer, and others, but the 

 consecutive stages in the nuclear disruption had not been seen. 



The second type of nucleus is particularly well marked in the group 

 of Sporozoa. Schneider as early as 1881 described the nucleus of 

 Klossia eberthi, one of the Coccidiida, as spherical, filled with " nuclear 

 sap" and inclosing a great "nucleolus," formed of a dense cortical 

 layer and a central alveolar portion. He observed no reticulum, but 

 recent observers, Mingazzini ('92), Labbe ('96), Siedlecki ('98), de- 

 scribed the nucleus of Coccidiida as containing a distinct reticulum, in 

 which granules of chromatin and achromatin (oxychromatin in various 

 stages of development) can be made out. Similar nuclei are found 

 among the Gregarinida (Wolters, '91; Marshall, '93 ; Siedlecki, '99). 

 The chief interest of these nuclei, however, centres in the chro- 

 matin mass, the " karyosome " of Labbe ('96), which, as in similar 

 nuclei among the Sarcodina, has been described under several names. 1 

 It colors so strongly with nuclear dyes that it often appears dense and 

 homogeneous (Fig. 135), but Schneider ('83), Labbe ('96), and Sied- 

 lecki ('98) agree that it is composed of at least two parts, an outer 

 cortical portion, thick and resisting in texture, and an inner granular 

 part. The cortical portion consists of chromatin with an exceed- 

 ingly fine alveolar structure, the thick walls of the alveoli being fre- 

 quently pressed so closely together that the striated appearance, early 

 described by Schneider, results. The internal granules, on the other 

 hand, take an intense acid stain, and are identified by Labbe as 

 oxychromatin granules. 



The history of this karyosome is strikingly similar to that of the 

 isolated chromatin mass in Cakituba. The observations of Siedlecki 

 and Labbe agree on this point, and a basis is thus secured for the com- 

 parison of these primitive nuclear changes. As in Calcituba, the 

 young sporozoite (A) has an homogeneous nucleus, i.e. a naked karyo- 

 some, but, in the epithelial cell of its host, it very quickly assumes 

 the adult structure (Siedlecki, '98). The intermediate stage between 

 the homogeneous nucleus and the formation of the intra-nuclear 

 karyosome has not been observed, but, as in Calcituba, the chromatin 

 reticulum presses more and more toward the periphery, where it is 

 finally condensed into the nuclear membrane. As the karyosome 



1 Chromatospherite of Schneider, Binnenkorper of Rhumbler and Schaudinn, Morulit 

 of Frenzel, Chromatin reservoir of Calkins, Karyosome of Siedlecki, Nucleolus of many 

 authors. 



