342 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
large, that several parts of the organization may be immediately : 
distinguished at first sight. Moreover numerous locomotive 
organs are very distinctly visible, although the motion in all the 
forms is exceedingly slow. I have gradually observed of these 
larger forms (even to one-fourth of a line in size) seventeen 
specimens (and recently seven more), all of which have been 
preserved alive in the sea-water at Berlin ever since the 22nd of 
September 1839. They belong to two different genera ; eleven 
specimens to a hitherto undescribed large species of the already 
known genus Geoponus (Polystomatium without umbilicus), which 
I call G. Stella borealis, and six to a species equally large of the 
known genus Nonionina, which I shall term N. germanica. The 
two genera Geoponus and Polystomatium, were called by D’Or- 
bigny Polystomella. They are represented in Plate V. and VI. 
It is at once evident that there is no outer body surrounding 
the shell, but only an interior soft one. The supposition that 
all these little animals, as asserted by D’Orbigny, or even as had 
been observed only in Sorites Orbiculus, possess an exsertile 
head with a plumose feeling and prehensile apparatus, such as 
the Flustre and Halcyonelle have, was not found to be confirmed. 
All the animalcules, even the most developed, of the two genera 
Geoponus and Nonionina, are, like those of Planulina and Tex- 
tilaria, without any prehensile apparatus at the head, and with- 
out any circle of feelers around the mouth. Each body is sur- 
rounded by the hard shell, has an ordinary simple aperture, 
and the numerous adhering bodies of Geoponus, whose social 
form (polypidom) resembles surprisingly the individual animals 
of Nonionina, have just as many visible simple apertures. On 
the other hand, the number of minute very extensile tentacula 
which at the same time effect the locomotion, and which project 
as it were from all parts of the sieve-like shell, evidently re- 
semble the contractile fringes of the Flustre and marine Gaste- 
ropodes. Their relationship to the pseudopodia [ Wechselfussen| 
of the Difflugie of Infusoria is indeed very great, as Dujardin has 
correctly observed ; but the rest of their organization, which this 
observer overlooked, removes them from the Infusoria quite as 
far as from a chaotic primitive substance. Great bundles of 
contractile filaments, arbitrarily ramifying (not as Dujardin as- 
serts actually, but merely apparently confluent), appear frequently 
to project from the umbilical district, where there are perhap 
distinct and larger contractile apertures. 
The foremost and largest cell of all the animals, sometimes thd 
