Relation between Nucleolus and Chromosomes. 47 
either that the plastin elaborated chromatin or more likely that chromatin 
extracted from the nuclear reticulum took lodgment there. The male pro- 
nucleus exhibits a similar structure (fig. 85). In both pronuclei the plas- 
mosome is lost shortly prior to fusion (fig. 86). All the evidence thus 
points to a very intimate physical and chemical relation between the linin, 
plasmosome, and chromatin nucleolus. I am inclined to the belief, in view 
of my results, that these three substances simply represent different stages 
in the process of elaboration of the same fundamental substance. 
In every full-grown oocyte are found usually one, sometimes several, 
masses of chromatin granules (figs. 31, 32, 33, 40). Generally these are 
in close proximity to the nucleolus (fig. 41), but frequently also removed 
at varying distances (fig. 38). Almost invariably this mass of granules 
is on that side of the nucleus nearest the periphery of the odcyte (figs. 37, 
49). In favorable cases I have been able to determine in it the character- 
istic dumb-bell shape of the definite chromosomes, only somewhat reduced in 
size. Again, in favorable sections I have been able to count approximately 
18 such individual bilobed bodies (figs. 40, 43). There is no doubt that 
these are the chromosomes which have persisted with identity unimpaired 
all through the growth-period and are now taking their position in proxim- 
ity to the nucleolus and periphery of the cell preparatory to maturation. 
Occasionally the chromosome group or strand lies closely connected with 
the nucleolus in the reticulum immediately surrounding it (figs. 37, 39, 41). 
This gives the appearance of a union with the nucleolus. Conklin (1902) 
describes very similar conditions in the maturing egg of Crepidula. It is 
doubtful if the chromosomes ever penetrate within the nucleolus, but they 
do often come into very close connection externally. In this state one can 
often see a portion of the mass extending beyond the border of the nucleo- 
lus, simulating an extrusion from the latter. Mathews (1895) mentions 
the presence of such a mass of granules in Asterias forbes, but beyond 
saying that it gives rise to the chromosomes of the first maturation spindle 
gives no further details. Bryce (1901) ventures the suggestion concerning 
a similar mass of granules in Echinus that it may possibly represent synapsis. 
Tennent (1906), on the other hand, suggests on the basis of experiments 
on eggs of Asterias forbesti subjected to CO, treatment and subsequently 
fertilized that “a conjugation or synapsis of egg chromosomes and sperm 
chromosomes takes place immediately before the formation of the equatorial 
plate of the first segmentation spindle” (p. 539). Judging from analogy 
with other forms where synapsis has been definitely observed, and on the 
strength of appearances in the youngest odcytes which seem to agree with 
the descriptions of early postsynaptic processes in some of these forms, I 
believe that in Asterias also true synapsis occurs some time during the telo- 
phase of the last odgonial division. The results above reported, I believe, 
justify the interpretation of this mass of chromatin granules as the persist- 
