488 MONTGOMERY. [Vol. XV. 



a number of constrictions, or buds of nucleolar substance may 

 project from its surface ; it may first break into two larger 

 pieces, and then these may fragment further, or it may at once 

 break into a number of pieces which are irregular in their 

 dimensions (Figs. 185-188, 190, 191, 193). These fragments 

 gradually wander apart from one another, the nucleus now 

 being larger and already somewhat irregular in shape ; and at 

 the same time each of the primitive nucleolar fragments divides 

 into smaller pieces of unequal size, until when the nucleus has 

 attained its greatest dimensions and most pronounced degree 

 of ramification it contains a very large number of irregular 

 nucleoli, which are unequal in their dimensions (Figs. 194- 

 196). The figures given of this last stage show only sections 

 of nuclei, and since as many as five or six sections may be made 

 of one of these colossal nuclei (my sections were between 3 and 

 5/x. in thickness), not one of these figures shows more than a por- 

 tion of the total number of nucleoli in these largest nuclei ; in 

 some of the latter nuclei I compute the number of the nucleolar 

 fragments to be at least three hundred. But the total mass of 

 nucleolar substance in these largest nuclei is certainly consid- 

 erably greater than the mass of the primitive nucleolus at 

 the time of its greatest size ; accordingly, though the division 

 products of the primitive nucleolus might constitute the greater 

 part of the nucleolar substance in the largest nuclei, they do 

 not constitute all of it. Therefore there must be a formation 

 of new nucleolar substance after the primitive nucleolus has 

 divided, i.e., a production of nucleolar substance not derived 

 from the primitive nucleolus ; I cannot determine the manner 

 of formation of this new nucleolar substance, but would suggest 

 that either new nucleoli are formed, or that the fragments of the 

 primitive nucleolus increase in size by the addition of new nucle- 

 olar substance to them. The greater number of nucleoli in the 

 largest nuclei are collected in or near the thicker portion of the 

 nucleus and few or none lie in the branched processes ; they are 

 at this time seldom in contact with the nuclear membrane. Only 

 a few of them contain vacuoles, and those which do may be re- 

 garded as derivatives of the primitive nucleolus, the vacuoles of 

 the latter still being preserved in its daughter-nucleoli. 



