1899] MULTINUCLEAR CELLS 437 



ance, but in the dermatogen cells vacuoles may be detected iu its 

 interior, it is immediately surrounded by a more or less broad invest- 

 ment of perfectly clear substance, the " Hof," which is sharply 

 marked off from the granular, peripheral nuclear substance. 



The first step in the division of such a nucleus is the division of 

 the nucleolus. Immediately after division the two nucleoli lie in one 

 " Hof." In the next stage that can be found each nucleolus is 

 surrounded by its own " Hof." This clear belt grows more and more 

 pronounced whilst the granular nuclear substance is gradually encroached 

 upon and finally forms only a peripheral investment to the clear balls 

 of substance which surround the nucleoli. The thin layer of granular 

 substance that lies between the two clear areas appears to disintegrate 

 or at any rate to separate without any previous constriction, and the 

 two spheres of clear substance, each containing a nucleolus, are 

 separated from one another and form the daughter nuclei. The clear 

 body-substance of these daughter nuclei becomes later more granular, 

 and the nuclei may move some distance apart. 



Observations show that it is not merely a question of the dis- 

 integration of the granular layer between the clear areas, but that there 

 is an actual strain pulling the nuclei in two. 



It should here be mentioned that every nucleus which is provided 

 with several nucleoli must not necessarily be regarded as indicating 

 a stage of nuclear fragmentation, although by far the majority of 

 resting nuclei have, in Zca, only a single nucleolus each. 



When older leaf -sheaths of Zca Mays are examined, nuclear frag- 

 mentations are seen, which differ considerably from those which have 

 been mentioned above, and conform much more nearly to the stages 

 which have been described in other plants by previous observers. 



The first and most obvious difference between direct nuclear 

 division in the younger and older cells of Zca is that whilst the former 

 takes place without the appearance of constrictions and changes of 

 form in the nucleus, the latter is conspicuously marked by the grotesque 

 intermediate shapes which that body assumes. 



The entire absence of constricting nuclei in the young leaf-bases, 

 which are obviously developing multinuclear cells, is the most 

 characteristic and at first the most puzzling feature about them. 

 Another point in which the older nuclei differ from the younger is that 

 in the former no constant relation between fragmentation and a pre- 

 ceding nucleolar division can be made out. Sometimes two or more 

 nucleoli appear here also, and one goes to each fragmentation product, 

 but just as often one nucleolus alone is present throughout the 

 process. 



These differences, which at a first glance are so striking, are 

 possibly associated with the alteration in constitution which the 

 nucleus suffers with advancing age. The young nucleus is large, and 

 has every appearance of being rich in water ; the nucleus of the older 



