Marcu 22, 1912] 
same physiologic and inheritance value as every 
other except perhaps for size or density. This con- 
dition parallels the general physiological condition 
in the plasmodroma whose protoplasm shows little 
differentiation for sensation, conduction, locomo- 
tion or specialized secretory activities, each bit of 
the protoplasm sharing in all these activities. In 
other protozoa we find several different types of 
more highly evolved chromatin structure. Some of 
these, as in Opalina, seem not in the line of evolu- 
tion of the metazoan condition. Others, as in 
Paramecium, have chromosomes which are linear 
aggregates of granules and which split longi- 
tudinally in mitosis. Such a form has a chromatin 
arrangement which would allow differentiation of 
the granules into divergent determiners, for a 
portion of each granule is given in mitosis to each 
daughter nucleus. 
A further discussion of this subject is in prepa- 
ration. Its place of publication is not yet de- 
termined. 
Opalina mitotica: MayNarp M. Metcar, Oberlin 
College. 
This paper, which was read by title only, will 
soon appear in full in one of the Spengel Fest- 
schrift volumes of the Zoologischer Jahrbiicher. 
The Pedogamous Conjugation of Blepharisma: 
Gary N. CALKINS, Columbia University. 
There is some question as to the specific name 
of the organism with which I am working. Up to 
the present I have followed Butschli in calling it 
B, musculus, identifying it with the form Urostyla 
musculus described by Hhrenberg. The name 
Blepharisma goes back only to Perty in 1849, who 
first used it as a generic name for a species of 
Spirostomum described by Ehrenberg again, as 
Spirostomum lateritia. Leaving for the present 
the taxonomic position of the organism I wish to 
speak here more particularly of some of the biolog- 
ical phenomena which have come under observation 
during the five months that I have kept Blephar- 
isma under culture. I isolated a specimen in July 
from pond water at Woods Hole and found that it 
lends itself readily to cultivation upon artificial 
media. For the best results a few drops of pond 
water plus a drop of 24-hour standard hay infu- 
sion are now used, a medium upon which the 
organisms have reached to-day the 160th genera- 
tion. None of the earlier observers made out a 
micronucleus and from total preparations alone I 
was unable to demonstrate it. Upon study of sec- 
tions of the organisms, however, I have been able 
to find structures which undoubtedly correspond 
SCIENCE 
469 
with a microneucleus in the typical ciliate. The 
macronucleus is large and comparatively easy to 
demonstrate, although it has a variety of forms; 
sometimes it is a single body of spheroidal form, 
again it breaks up into irregular fragments. On 
division there are two chief portions, one at 
either end, and a connecting strand of some- 
what different texture and the micronuclei are 
connected with this. It is the custom of all who 
carry on careful culture work to isolate one indi- 
vidual and supply it with fresh medium every day. 
The individuals left over after isolation of the one 
specimen are placed in larger vessels and kept as 
“¢stock.’’? Early in the summer it was seen that 
endogamous conjugations occurred frequently in 
this stock material, in some cases reaching the 
proportions of a general epidemic. So keen at 
times is this ‘‘sexual hunger’’ as Maupas called it, 
that conjugation occurs between the closest re- 
lated cells. For example an individual was iso- 
lated in the 104th generation, fresh medium and 
food being given as usual. On the following day 
it had divided, but the two sister cells were united 
in typical conjugation. This, I believe, is the 
closest relation on record for pedogamous con- 
jugants amongst Infusoria. The cells begin to 
conjugate at the anterior tips as in Paramecium 
and gradual fusion extends along the peristome 
for about two thirds of the length and never 
further, thus leaving the greater portion of the 
undulating membrane and the mouth entirely free. 
They remain in conjugation from 12 to 24 hours 
and separate through vacuolization of the connect- 
ing zone of protoplasm. The most remarkable 
phenomena are connected with the nuclear rela- 
tions during conjugation on which I can now give 
only fragmentary notes, as my observations are 
not completed. The macronucleus becomes com- 
pact and spheroidal with a typical ‘‘kernspalt’’ in 
the center. It is also enclosed in a firm resistant 
membrane like a cyst, a structure which does not 
exist at other times. Sections of conjugating pairs 
show that the nucleus is made up at this time of 
two main bodies of chromatin of densely granular 
appearance, while between them long drawn-out 
rods of chromatin like chromosomes appear 
to be dividing. This central material gives 
rise to two smalleg nuclei which are freed from 
the mass of macronuclear material and in the 
cytoplasm undergo one or two further divisions 
which result in the gametic nuclei. I have not yet 
found the pronuclei in the process of fusion, but 
have seen them in the connecting bridge between the 
