222 



BIOLOGICAL LECTURES. 



It is a temporary stage like this in Tctramitus or Paramceba 

 that lends support to Schaudinn's alternative. Intermediate 

 stages between this condition and the permanent intranuclear 

 sphere may be seen in numerous flagellates, such as CJiilotiionas 

 and some species of Ti-achelomonas, where no nuclear mem- 

 brane surrounds the chromatin granules. On the other hand, 

 it cannot be denied that there is very strong evidence for Hert- 

 wig's view in the observations of Schaudinn upon the nuclei 

 of Foraminifera,! and of Siedlecki upon Coccidiida.^ In both 

 cases the nuclei first appear as solid masses of chromatin, with 

 (Coccidiida) or without a nuclear membrane. These become 

 vacuolated in Foraminifera, and membrane and nuclear reticu- 



FiG. 4.— Formation of nuclear membrane and reticulum from the chromatin of an originally 

 homogeneous chromatosphere in Calciizcba (after Schaudinn). 



lum, as well as the definitive chromatin, are all derived from the 

 homogeneous chromatosphere (Fig. 4). There is no mitotic 

 figure, however, the chromatin fragmenting by what Schaudinn 

 calls "multiple nuclear division," and the sphere, as such, does 

 not appear in either case. 



Even in the lowest forms the sphere apparently exerts some 

 force of attraction, perhaps chemotactic, upon the chromatin, 

 and this force may or may not be strong enough to keep the 

 granules permanently aggregated ; if not, the distributed nucleus 

 results ; if so, the intranuclear condition of the sphere is the 

 outcome. In Paramceba, Noctiluca, in diatoms, and in the 

 majority of the Metazoa and plants, a nuclear membrane is 

 formed, and the sphere remains outside of the nucleus. As a 



1 Biol. Centralbl., 1894, Bd. xiv. 



- Aim. d. riust. Pasteur, tome xii, 1S98. 



