GENERAL CONCLUSTONS. 45 



rangement. This at any rate is my view for the Peripatus 

 nucleus. 



Klein figures (10, PI. 18) nuclei from the epidermis of the 

 newt in a state of direct division. These figures resemble very 

 closely some of the endodermal nuclei in the gastrula of Peri- 

 patus. 



Klein is still more explicit as to the continuity of the nuclear 

 and extra-nuclear reticulum in his second communication ou 

 this subject (11, p. 416). 



Unfortunately I have not been able to see the papers of 

 Strieker and Heitzmann. 



Leydig in his latest communication (12) regards the spindle- 

 fibres as parts of the ordinary reticulum (spongioplasma he 

 calls it) with much elongated meshes (p. 9). He further looks 

 upon the nuclear membrane as merely the outer portions of 

 the nuclear network, and describes it as being porous, and 

 takes the same view as Klein with regard to the continuity of 

 the nuclear and intra- nuclear network. 



Leydig also describes some accessory nuclei as occurring 

 in certain cells. These are smaller than the main nucleus and 

 stain less deeply. It is possible that they are structures of 

 the same nature as those described above in the endoderm of 

 Peripatus {vide pp. 26, 27). 



He refers, in this connection, especially to the small acces- 

 sory nuclei which are found in many Protozoa, and which, 

 according to Gruber (3) and Jickeli (7), are for the most part 

 derived from the breaking up of the main nucleus. The parti- 

 cles resulting from this fragmentation of the nucleus seem 

 eventually to come together again to form a new main nucleus. 

 One would like to have some more details about this peculiar 

 process in Infusoria, derived if possible from the study of 

 sections. The term " fragmentation," which is applied to it 

 apparently because the chromatic parts of the nucleus become 

 separated from one another and scattered throughout the 

 animal, seems to imply a distinct breaking up into small 

 isolated portions. If this really happens the nucleus of Infu- 

 soria must differ from most other nuclei in which the chromatic 



