V. //. Blackman. 
COCCOLITHS AND COCCOSPHERES. 
By V. H. Blackman. 
155 
A LTHOUGH the curious structures known as Coccoliths were 
first observed in 1836 , yet the exact nature of the organisms 
from which they are derived has remained unsettled till the 
present year. They were first described by Ehrenberg in various 
chalk formations, as minute round or oval calcareous plates, and 
considered to be of inorganic nature. About twenty years later, 
however, Huxley and Wallich observed similar structures in deep 
sea deposits, obtained from the North Atlantic in connection with 
the laying of the first cable between Europe and America. Huxley 
gave them the name of Coccoliths, on account of their resemblance 
to a Protococcus cell, while Wallich observed that in the deep sea 
ooze they were sometimes found aggregated into spherical masses, 
which he called Coccospheres and rightly considered to be the 
organisms from which the Coccoliths had been derived by the 
separation of the plates of the skeleton. The Coccospheres them¬ 
selves, however, he considered to be mere developmental stages of 
Foraminifera. A few years later the same worker made the 
important discovery that not only were Coccospheres to be found 
in the chalk (as Sorby had in the meantime observed) and in deep 
sea deposits, but also floating free on the surface in tropical waters. 
It was thus clear that Coccospheres were very ancient forms and 
of much scientific interest on account of the part which they have 
played in the production of the chalk and the part they still play in 
the formation of deep-sea deposits. 
Wallich described two species of Coccosphnera, and on the 
Challenger expedition Coccospheres were met with in most waters, 
except polar ones, together with forms bearing plates of a different 
shape, to which the name of Rhabdospheres was given. It seemed clear 
that the Coccospheres and Rhabdospheres were unicellular organ¬ 
isms, but as nearly all observations had been confined to the calcareous 
skeleton, there was very little evidence as to their systematic position, 
and the strangest views as to the nature of the Coccoliths were put 
forward; the actual existence of Coccospheres being doubted by 
many who had failed to find them. John Murray had suggested that 
the organisms in question were of algal nature and this was sup¬ 
ported by the discovery, in 1897 , of a yellow green chromatophore in 
CoccospJiaeva leptopora by George Murray and Blackman. The small 
size ( 10 - 30 /x.), however, of these organisms renders their capture very 
difficult, for the finest miller’s silk available for nets has a mesh of 
