F. Cavers. 275 
THE INTER-RELATIONSHIPS OF PROTISTA AND 
PRIMITIVE FUNGI. 
By F. Cavers. 
(Continued from p. 227). 
The genus Labyrinthula includes two marine species (L. vitellina, 
a yellow form, and L. macrocystis, colourless, both discovered by 
Cienkowski in 1867) and a freshwater species (L. cienkowskii, very 
similar to L. macrocystis , discovered by Zopf in 1892); all three are 
parasitic on algas. In the active phase the organism consists of 
uninucleate protoplasmic units joined into a network by sparingly 
branched and anastomosing pseudopodia, so that it presents a 
striking but purely superficial resemblance to Chlainydomyxa. On 
encystment, which occurs as a result of drought, the amoeboid units 
become closely aggregated and each secretes a cyst wall, while in 
L. macrocystis a firm common envelope is then formed in which the 
encysted units are enclosed. In L. cienkowskii the contents emerge 
from the cyst as a single mass, but in the other two species the 
contents divide into four within the cyst, in all cases becoming 
amoeboid and undergoing division by binary fission so as to increase 
the number of units in the colony, though according to Zopf the 
amoebulae on leaving the cysts may become joined up by their 
pseudopodia. Zopf distinguished the colony of Labyrinthula as a 
“ thread-plasmodium,” and regarded it as intermediate between the 
“ pseudoplasmodium ” of the Acrasieae (see below, amoebulae apposed 
but maintaining their distinctness) and the true plasmodium of the 
Myxomycetes proper (complete fusion between the uniting 
amoebulae), but (especially as Zopf only inferred fusion between the 
amoebulae from observing on one occasion in L. cienkowskii three 
empty cysts with three units in their neighbourhood) there does not 
appear to be much point in this suggestion. The Labyrinthula 
colony may equally well be compared with that seen in primitive 
Foraminifera like Mikrogromia, near which, in the absence of further 
details of its life cycle, the genus may perhaps be provisionally 
placed. 
The affinities of the Sporozoa may be briefly considered here, 
for there seems little doubt that this group has, in part, arisen from 
the Proteomyxa along the same line as that which has given rise to 
the “ primitive fungi ” with which we are now more directly 
concerned. As already mentioned, the Sporozoa were divided by 
Metschnikoff into Ectospora and Endospora, and recent work on the 
group has shown that these two divisions are probably not related 
phylogenetically but are of quite different origin ; that is, the group 
is an artificial one and includes two independent series of parasitic 
Protozoa, the general resemblances between them being due to 
convergence brought about by their specialised mode of life. That 
the Ectospora (Gregarinida, Coccidia, Haemosporidia) are derived 
from Flagellata is indicated by the actual ontogenetic connexion 
known to exist between certain Haemoflagellates and certain 
Haemosporidia; the possession by many Coccidia of biflagellate 
microgametes resembling in structure the heteromastigine 
Flagellates; the possession by various typical Flagellates (e.g., 
Herpetomonas) of an attached resting-phase when the parasites 
