14 SCHULTZE, ON DIATOMACES. 
induced me then to make further researches among other 
Diatoms, where they had been observed by G. Wagener, also 
in Coscinodiscus, and finally I saw them in a large Denticella. 
Great transparency of the siliceous coats is necessary for a 
clear observation of the streams of granules. Those forms 
of Coscinodiscus the sculpture of whose shells is very delicate, 
as C. centralis, Ehrbg. (‘ Micro-geologie,’ tab. xxu, fig. 1), 
with which a form common at Heligoland agrees, are 
consequently more fitted than others, such as C. radiatus 
and C. patina, Ehrbg., which are finely marked, and possess 
an opaque, sharply sculptured shell. For the same reason 
Triceratium, of which many species occur at Heligoland, is 
not adapted for observation. In several Diatoms placed 
together, whilst living, in a fluid adapted for the preservation 
of Meduse,* could be observed, im addition, a radiate, 
threaded arrangement of the organized contents, corre- 
sponding with that in which the granular streams would have 
been observed in life, as, for instance, in the large trans- 
parent Navicula angulata. 
The whole movements I have seen neither in Rhizosolenia, 
nor in Cosinodiscus and Denticella. The internal move- 
ments are of the following kind : 
Coscinodiscus and Denticella (figs. 11—13) show, in the 
living state, a nucleus placed almost in the centre, but still 
drawing near to one of the side walls ; it 1s a round, colourless 
vesicle, of the size of a human blood-corpuscle, with a large, 
strongly refracting nucleolus—it might be taken for a cell 
with a nucleus, but which last would then want the nucleolus. 
Around this body is found an accumulation of a finely 
granular colourless mass, from which radiate a multitude of 
finer and coarser cords, passing through the internal space of 
the Diatoms, which is of a water-like clearness, in all direc- 
tions. They all come to an end at one of the surfaces 
of the siliceous covering, lying closely round an exceedingly 
* This fluid, consisting of common salt Ziv, alum 3ij, sublimate gr. iv, 
dissolved in two quarts of distilled water, is well adapted for the preserva- 
tion of small organisms, procured by fishing with the fine net in the sea. 
One rinses out the corner of the net in a glass filled with this solution in- 
stead of sea-water. In this manner, after several repetitions, one obtains 
a sediment which may serve as a mine for the whole year. Noctiluca, 
Echinoderm, and Annelid larvee, Entomostraca, Diatoms, Polythalamiz, and 
Polycystiniz are admirably preserved, both in their soft parts as well as 
their hard structures. To make them transparent, glycerine should be 
afterwards added. In the circumnavigation of the world, glasses containing 
this fluid, each filled at different places and noted, would furnish richer and 
better material for the study of geographical distribution and variety of 
forms than searching the stomachs of animals or the filtering of several 
bottles brought back filled with sea-water. 
