54 Papers from the Marine Biological Laboratory at Tortugas. 
same series of eggs. In one type the chromosomes arose from the nuclear 
reticulum (here the nucleolus was a plasmosome), in the other from a 
chromatin nucleolus. Asterias presents no condition which can be reconciled 
with either of the types described and figured by Wilson. 
Max Hartmann (1902) concludes for Asterias glacialis that “ during the 
growth-period of the ovarian eggs there occur ‘ vegetative nuclear altera- 
tions,’ the distribution of chromatin substance in the nucleus, and accumula- 
tion of the same in the nucleolus. At the end of this period all the 
chromatin and plastin is combined in the nucleolus, and out of this there 
arise at the time of the shedding of eggs into the water with the appearance 
of an astral structure and dissolution of the germinal vesicle, the chromo- 
somes of first maturation division.” 
K. Guenther (1903) reports the following in the case of Psamechinus 
microtuberculatus and Holothuria tubulosa: “ Der Nucleolus stellt einen vom 
Kerngertist ausgeschiedenen Tropfen, in den das Chromatin hineindringt um 
sich in ihn zu sondern und fiir seine Theilung zu ordnen,” p. 23. He holds 
that the chromatin of the germinal vesicle is collected and stored in the 
nucleolus during the growth-period of the odcyte, that it undergoes there 
possibly some physical and chemical changes, and so wanders forth again 
at the time of maturation to give rise to the chromosomes of the first divi- 
sion. He remarks further that the ‘‘ Chromatinfaden (hat) bei seinen Aus- 
wanderung eine kleine Vacuole zurtickgelassen, und wenn nun bei diese der 
Kernsaft eintritt, so ist am Raum nicht verloren.” 
T. H. Bryce (1903) states that in Echinus esculentus “the chromatin 
substance is at first confined to the nucleolus, and later leaves it to form the 
chromatin basis of the nuclear network as a whole and therefore also of the 
future chromosomes,” but adds that the nature of his material makes it 
impossible for him to deny or affirm the direct origin of the chromosomes 
from the nucleolus: 
My own observations on the eggs of Asterias forbes establish beyond 
a doubt, I believe, the fact that while the chromosomes often appear to 
arise from within the nucleolus, as described by Hartmann (1902) and Guen- 
ther (1903) in certain echinoderms, they never really penetrate beyond the 
surface of the nucleolus, at least to the extent that their individuality is lost 
and their substance merged into the common chromatin substance of the 
nucleolus. Study of the different stages throughout the growth-period 
shows that the chromosomes always retain their identity, though they are 
greatly decreased in size, and they mass together into a clump which often 
attaches itself closely to the nucleolus, from whence the chromosomes pass 
into the spindle during early stages of maturation. This phenomenon of 
chromosome disposition is very similar to what Conklin (1903) has described 
in Crepidula and Lillie (1906) in Chetopterus. According to the former, 
“the chromosomes, which are at first widely scattered through the nucleus, 
