Relation between Nucleolus and Chromosomes. 65 
main processes, but a slight variation in details, together with a non-corre- 
spondence in the time of occurrence of the successive stages. 
On the question of the individuality of the chromosomes Hipponoé yields 
no positive results. Even in the late growth-period there is no indication 
of chromosomes as such. And it is clear that at least a large part of their 
chromatin is either contributed by the disappearing nucleoli or elaborated 
by the cell protoplasm. Hipponoé supports the conclusions drawn in regard 
to the function of the nucleolus in the case of Asterias, that it serves in part 
at least as a storehouse of nutritive material contributed to the chromosomes 
prior to maturation. 
SUMMARY OF RESULTS ON ASTERIAS FORBESII. 
I. Synizesis occurs in the odcyte of the first order at the very begin- 
ning of the growth-period (size of nucleus 5 microns). 
2. The growth-period is passed through rapidly. The single spireme of 
the contraction phase becomes double and segments into a number (18?) of 
irregularly shaped chromosomes. ‘These decrease in size and collect in one 
or several masses of minute bilobed bodies in close proximity to or upon 
the nucleolus. 
3. During the latter half of the growth-period all the chromatin, with the 
exception of what is held by the chromosomes, becomes stored in the en- 
larging nucleolus, the linin meshwork of the nucleus being left entirely 
achromatic shortly prior to maturation. 
4. The nucleolus consists of a plastin ground-substance infiltrated and 
covered over with chromatin. In the living condition of the odcyte the 
nucleolus appears vacuolated. The “ vacuoles” are spherules of fluid chro- 
matin, and where these are filled, properly stained sections reveal a homo- 
geneous structure of the nucleolus. Linin, plastin ground-substance, and 
chromatin appear to represent closely related substances, possibly different 
phases of elaboration of the same fundamental material. 
5. The chromosomes do not arise out of the nucleolus. The latter con- 
tributes nutritive substance to them, by virtue of which they increase slightly 
in size before entering the first maturation spindle. 
6. The number of chromosomes in the prophase of the first polar mitosis 
is 18. They vary somewhat in size (one is considerably larger than the 
rest), all have a characteristic dumb-bell-shaped appearance, and some are 
clearly double (bivalent). 
7. The two maturation divisions effect a double longitudinal fission of the 
original bilobed chromosomes. The reduced number of chromosomes is 
again 18. 
8. Observations on Hipponoé esculenta agree in essential points with 
those made on Asterias forbesti and support the conclusions regarding the 
origin of the chromosomes, the function of the nucleolus, and the reduc- 
tion phenomena. 
