594 
T. H. MORGAN 
1. CENTRIFUGING THE EGG OF CUMINGIA 
When I began the study of the effects of centrifuging the eggs 
of Cumingia tellinoides in the summer of 1907, my object was 
to compare the results with those already obtained by Lyon and 
myself on the eggs of the sea urchin. At that time the observa- 
tions of Conklin and of Lillie had drawn attention to the role 
of the visible materials of the egg as organ-forming. Although no 
evidence of the formative nature of the visible substances in the 
egg of the sea urchin could be obtained by the centrifuging experi- 
ment, it did not follow that in eggs with a precocious type of 
cleavage, such as Conklin and Lillie studied, visible organ-forming 
materials might not be present. I therefore took up the examina- 
tion of Cumingia to test the question in the group of molluscs 
that shows the characteristic precocious type of development. 
In addition, I wished to study the effects on the karyokinetic 
division of the egg ; for, it became manifest at once that the cen- 
trifuge furnishes an instrument of wonderful delicacy by means of 
which the parts of the egg may be shifted in regard to each other 
without destroying the power of development of the egg. At 
that time I was hopeful that at some stage in the karyokinetic 
process it might be possible to move the chromosomes, and in 
this way study the influence of the chromosomes on development. 
With this end in view every stage of the egg from the time of dis- 
appearance of the germinal vesicle to the four-cell stage has been 
centrifuged, but without in any case affecting the separation or 
scattering of the chromosomes. This attempt has consumed a 
good deal of time, and while the results are negative so far as the 
separation of the chromosomes is concerned, other important 
questions have arisen and some light has been thrown on the na- 
ture of the karyokinetic process. 
I wish to express to Professor Oilman A. Drew my obligations 
for bringing to my attention the possibilities of the Cumingia 
eggs, and the method which he had worked out of procuring them 
in abundance. During June, July and August, when this little 
bivalve is brought in from the mud in which it lives and put into 
dishes of water, it begins after about half an hour or less to set 
free its eggs or its sperm, according to sex. 
