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TETRAEDROIDES SPETSBERGENSIS GEN. ET 
SP. NOV., A NEW ALGA FROM SPITZBERGEN 
(RESULTS OF THE OXFORD UNIVERSITY EXPEDITION 
TO SPITZBERGEN, No. 28) 
By B. MILLARD GRIFFITHS, M.Sc., F.L.S. 
I N the material collected by Mr Summerhayes during the Oxford 
University Expedition to Spitzbergen in the summer of 1921, an 
alga occurred which is apparently a new genus. It was found among 
the stems of a moss in a crevice of rock on Bear Island, and was 
associated with a few small diatoms and much vegetable detritus 
from the plants among whose stems it grew. 
At first glance the alga resembles a species of Tetraedron, but closer 
examination shows that the plant is not unicellular but consists of 
at least two cells and in some cases of even three or four. The thallus 
of the commoner bicellular type is pyriform, bipyramidal or ellip¬ 
soidal with slightly truncated ends (Figs. 1-7). The exterior walls 
of the cells are thick but the interior transverse wall is thin. Other 
two-celled forms are tetrahedral or pyramidal or irregularly poly¬ 
hedral with very thick exterior walls (Figs. 8-11). As a rule, one or 
more angles of the polyhedron are distinctly flattened at the apex. 
More rarely polyhedral thalli consisting of three or four cells occur 
(Figs. 12, 13); in these cases also, the exterior walls are thick and the 
interior walls are thin. 
Vegetative reproduction takes place by a kind of incipient thread 
formation. One or both cells of the thallus grow out into thin-walled 
tubular extensions (Figs. 14, 15, 16). The tube divides primarily 
by a series of constrictions, and each segment is again divided into 
two cells by the formation of a thin transverse wall. The primary 
constriction may be complete, in which case the end of the resultant 
thallus is sharply rounded off, or after constriction has partly taken 
place, the final division is accomplished by the laying down of a thick 
transverse wall which splits and sets the pairs of cells free. In this 
case the resultant thalli have the truncated apices to which reference 
has been made. 
In Fig. 17 is shown an apparently abortive attempt at the forma¬ 
tion of an incipient thread of about seven cells, of which the three 
lower have failed to mature. The upper part of the thread shows the 
