60 Papers from the Marine Biological Laboratory at Tortugas. 
The fact that the early segmentation stages give a chromosome count in 
the prophase of approximately 36 indicates that the 18 bilobed chromo- 
somes of the first maturation prophase are mostly, if not entirely, bivalents. 
Moreover, their double character is occasionally plainly evident (figs. 64, 65). 
However, since synapsis could not be observed, no conclusive evidence 
appears as to the valency of the chromosomes, nor as to whether the chromo- 
somes coupled endwise or sidewise, nor in which direction the condensa- 
tion occurred to give rise to the bilobed form; hence no positive statement 
is justified as to whether the reduction is quantitative or qualitative. If the 
chromosomes fused side by side in synapsis and the bivalents were so trans- 
formed into a bilobed body that each globe can be represented by AB, then 
the double longitudinal division effects a true reduction, and the resulting 
chromosomes are A’s and B’s. If one globe represents A and the other B, 
then the resulting chromosomes are AB’s. Similar possibilities result froma 
double longitudinal division if the synapsis was endwise. 
FUNCTION OF THE NUCLEOLUS. 
As to the function of the nucleolus in the germinal vesicle, besides giving 
rise to the chromosomes, various opinions are held by different writers, some 
ascribing to it an incidental role in conjunction with chromosome formation, 
others a very definite role exclusive thereof. I shall not undertake to give a 
full discussion of so complicated and difficult a subject. I desire merely to 
call attention to a few of the most divergent views in regard to this enig- 
matical cell-constituent and harmonize my own observation with one or the 
other of these. 
Pfitzner (1883), basing his opinion on his investigation of the ectodermal 
cells of Hydra, makes the generalization that the nucleolus has merely a 
passive function in mitosis: “ die einer aufgespeicherten Nahrungs-materials 
zur Neubildung von Chromatin.” He terms the nucleolar substance “ pro- 
chromatin,” since he finds that in mitosis it changes into chromatin. 
Schneider (1901) thinks that the large nucleoli of echinoderm eggs are 
but reserve masses of chromatin. The experiments with artificially fer- 
tilized echinoderm eggs by R. Hertwig (1895) and Wilson (1901) seem to 
confirm the validity of Schneider’s view, at least under certain conditions. 
Khumbler (1893) says: “ Mir scheinen die Binnenkorper (nucleoli) Reser- 
vestoffe darzustellen, die fiir Zeit aufgespeichert werfen, wo die Theilung 
eine grosse Zunahme des Vererbungs Apparates bez. des Idioplasm im Sinne 
Weismann’s erfordert, wo aber diese Stoffe nicht rasch genug durch die Zell- 
membran hundurch Nahrung finden kénnen.”’ 
Hacker (1895) states that in 4!quorea and in various annelids and echino- 
derms “ the nucleolus is cast out bodily into the cytoplasm, afterwards lying 
there for some time as a ‘ metanucleus’ before degenerating. In these cases 
the chromosomes are formed independently of the nucleoli . . . it seems 
