THE GERMINAL SPOT IN ECHINODERM EGGS. 
By H. E. Jorpan. 
The object of this paper is to report the results of further studies of the 
prematuration stages of echinoderm eggs. The main problem involved is 
to determine the relation of the nucleolus to the chromosomes during the - 
growth-period. I have recently shown that in both Asterias forbesii and 
Hipponoé esculenta the chromosomes for the first maturation mitosis arise 
from the nuclear reticulum with some variation of details in the two species.t 
In Asterias forbes the chromosomes subsequent to origin assume a more 
or less intimate connection with the nucleolus just prior to maturation, and 
the nucleolus, after passing through a preliminary process of fragmenta- 
tion, apparently contributes chromatic material to the chromosomes. In 
Hipponoé esculenta the relationship between nucleoli and chromosomes—if 
indeed one exist at all—is more obscure, but the nucleoli here also disappear 
about the time of maturation. The ultimate aim of these studies is to obtain 
some information regarding the function of the germinal spot. 
I am now able to report upon two additional species of echinoderms, 
one again a star-fish (Echinaster crassispina) and the other a brittle-star 
(Ophiocoma pumila). The latter appears to agree rather closely with what 
obtains in Hipponoé and with what Wilson? reports of some of the sets 
of eggs of Toxopneustes variegatus treated with MgCl,; while Echinaster 
presents a case unique in that the chromosomes here appear to arise as the 
direct products of nucleolar fragmentation. I regret that my material does 
not yield stages for the study of either the odgonial history or the matura- 
tion mitoses, but the various stages of the growth-period, which are repre- 
sented in great variety and abundance, give conclusive results in regard to 
the essential point, 7. e., the origin of the chromosomes. I trust the com- 
ing summer will yield the stages desired for a more complete study of the 
odgenesis of these highly interesting forms. 
The material at my disposal was collected during a brief stay at the 
Marine Biological Laboratory of the Carnegie Institution of Washington, 
*Jordan, H. E., 1908. The relation of the nucleolus to the chromosomes in the 
primary oocyte of Asterias forbesii. This volume, p. 39. 
* Wilson, E. B., 1to901. A cytological study of artificial parthenogenesis in sea- 
urchin eggs. Arch. Entwickl., Mech. Bd. 12: 529. 
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