533 
Herrn Prof. Dr. H. Joseph, Wien, spreche ich fiir die Anferti- 
gung der Photographien meinen besten Dank aus. 
Literaturverzeichnis. 
. Eschscholz, System der Acalephen. 1829. 
. Haeckel, Monographie der Medusen. 1880/1881. 
A. G. Mayer, Medusae of the world. Vol. III. The scyphomedusae. 1910. 
E. Vanhöffen, Untersuchungen über semäostome und rhizostome Medusen. 
Bibl. Zoolog. Bd. 1. Heft 3. 1888. 
2. Notes upon Opalina. 
By Maynard M. Metcalf. 
(With 21 figures.) 
eingeg. 9. April 1914. 
I. Chomosomes in Opalina. 
Thru the kindness of Professor E. A. Andrews, I received some 
time ago half a dozen live toads, Bufo agua, collected in Jamaica in 
connection with the summer laboratory of the Johns Hopkins University. 
In the recta of these animals were large numbers of a good-sized Opa- 
lina, a new species which has proven remarkably favorable for study of 
nuclear phenomena. Opalina antilliensis, as I am naming it, is a large 
flat species, as flat as O. ranarum. It is one of the binucleated forms 
and its nuclei are huge, tho not so large in comparison with the body 
as are those of O. macronucleata described by Bezzenberger. Raff’s 
O. binucleata, according to published measurements, tho not from the 
figures, has nuclei of about the same size as those of O. antilliensis. 
Figures 12 and 13 show two nuclei of O. antilliensis magnified 1780 
times. One realizes their large size upon comparing with figs. 14 to 21 
which represent nuclei of an undescribed Opalina (O. intermedia) mag- 
nified to the same degree as those shown in figs. 12 and 13. The latter 
nuclei are of the size of those seen in the well-known O. ranarum. The 
nuclei of O. antılliensis are three times as wide, as those of the multi- 
nucleated Opalinas, in corresponding condition. 
The diameter of the nucleus is but very little less than the thickness 
of the whole ectosarc (fig. 3). It is unnecessary, therefore, to make 
sections for the study of nuclear phenomena, for in total preparations 
there is only the ectosarc tissue above and below the nuclei, and this 
does not at all obscure vision. The chromatin in each nucleus is not 
abundant for the size of the nucleus and, as in all binucleated Opalinas 
studied, is loosely arranged at the surface of the nucleus, just beneath the 
membrane. These conditions make the nucleus of Opalina antilliensis by 
far the clearest finest nucleus for study I have seen among the Opalinas, 
or in the whole group of the Protozoa. Doubtless the nuclei of O. binu- 
