SCHULTZE, ON DIATOMACL&. 13 
The description follows the appearances, as seen in passing 
the eye over a thin section from the circumference to the 
centre. 

Prenomena of InrerNaL Movemunts in Diatomacra of 
the Nortn Spa, belonging to the GENERA CosciINopIscus, 
DentIcELiaA, and RutzosoLtenta. With a Plate. By Pro- 
fessor Max ScHuULtzeE. 
THe sea around Heligoland is rich in large Diatoms, 
which are frequently brought up in considerable numbers by 
the fine net. Several of the species very abundant there 
have been found by Ehrenberg at Cuxhaven, as Coscino- 
discus, Zygoceros, Eucampia, Triceratium (‘Abhandl. d. Akad. 
d. Wiss. z. Berlin,’ 1839). Others are still not known out 
of that region, as Chetoceros (Brightwell, ‘Quart. Journ. of 
Micr. Science,’ 1856, p. 105, tab. vii), Denticella, Rhizoso- 
lenia. 
By far the most numerous forms of the genus last named 
occurred towards the end of the autumn. The Rhizoso- 
lenia are readily to be distinguished with the naked eye, and 
were wanting on no day in the excursions undertaken im com- 
pany with my father and the Messrs. G. Wagener, Lieber- 
kthn, and Kupfer. In a glass containing them one 
perceives, by transmitted sunlight, a glittering, proceeding 
from small rods of a hair-like fineness, which refract and 
bend the light, like crystals of Cholesterme, but more 
strongly, so that they shine in all the colours of the rainbow. 
The rods not unfrequently attain the length of 2 to 3 lines. 
Perfect examples of the genus Khizosolenia Khrbg., so 
far as I am aware, have only been found by Brightwell up to 
the present, and were first mentioned in No. XX of the 
‘ Quart. Journ: of Micr. Science,’ 1857, p. 191, and were 
afterwards figured in the later numbers of the same 
Journal. These ‘being all procured from the stomachs of 
Ascidians and Salpze, as also from Noctiluca, were seen filled 
in part with organic, but not living, contents. Still, Bright- 
well, in the last-mentioned place, states, from his own obser- 
vation, that Rhizosolenia setigera shows a movement like 
other Diatoms, in which the tubes push themselves slowly 
backwards and forwards. Here also it is mentioned that 
Rhizosolenize occur freely, swimming in the seas of warmer 
latitudes. 
Herr G. Wagener first drew my attention to the peculiar 
currents of granules occurring in the Rhizosoleniz, which 
