PROTOZOAN NUCLEI. 381 



such a scale, but the series appHes only to the nuclei during 

 division while the nuclei at rest are quite different, and the cell- 

 bodies to which the nuclei belong, often represent widely separ- 

 ate classes of animals. A phylogeny based upon such a foun- 

 dation must necessarily be weak, for it is perfectly possible that 

 various classes of Protozoa may develop mitotic modifications 

 quite independently of each other and yet along the same lines. 



In view of the fact that the nuclei of the Protozoa show such 

 wide differences it is not surprising that some forms should pos- 

 sess no structures which can be accurately defined as nuclei. 

 Indeed, if the nucleus be regarded merely from a morphological 

 standpoint it is quite easy to conceive of cells which possess no 

 nuclei (Haeckel's Monera, in part) and to imagine groups of cells 

 intermediate between such forms and those in which a definite 

 morphological nucleus can be made out. These intermediate 

 forms are the subject of the present paper. 



The observations were made on various Protozoa including 

 simple flagellates, dinoflagellates, rhizopods, heliozoa, ciliates, 

 suctoria and Noctiliica. The material was fixed with sublimate 

 acetic (5 per cent, acetic), picro acetic, Hermann's fluid, and 

 saturated sublimate. The stains used were mainly iron haema- 

 toxylin with orange or Congo red, and the Flemming triple. 

 The nuclei were studied from thin sections or from total prepara- 

 tions, sections giving the best results. 



The So-called " Distributed Nucleus." 



A number of forms which Haeckel included in his enucleate 

 Protista, have subsequently, by the use of better optical instru- 

 ments and improved technique, been found to contain minute 

 particles of chromatin which are distributed without definite or- 

 der throughout the cell. Such types have been called distributed 

 nuclei. Occasional instances of this type of nucleus have been 

 found in nearly every group of Protozoa. In the Ciliata, 

 Gruber ('84) found that Chcenia teres and Traclicloccrca pJiccnicop- 

 teriis possess no true nuclei but minute granules of chromatin 

 distributed throughout the cell-substance. These granules, ac- 



