FILAMENTOUS THALLUS OF DUMONTIA FILIFORMIS. 441 
Fr. Schmitz’s views on the structure and development of the 
Floridean thallus, as quoted above, for it has arisen entirely 
(taking the typical endogenous mode of origin) by intercalary 
division of the articulations (‘‘ Quertheilungen der einzelnen Glie- 
derzellen ”’) of the filaments. It is somewhat doubtful whether 
his generalization could legitimately be expected to include such 
an exceptional case, the first of its kind published, so far as 
could be ascertained. On the other hand, the subsequent deve- 
lopment of the filiform thallus agrees in essential points, so far 
as was observed, with his generalization: that is, this thallus and 
its branches grow in length by the transverse acropetal division 
of an apical cell, and the segments cut off from the same do not 
divide by an axially median longtuidinal wall, nor in an intercalary 
manner. 
The creeping thallus, when found growing on other alge, 
instead of the more usual rocky substratum, is attached to its host 
by more or less conical plugs of tissue, which penetrate the latter 
and destroy its cells, as they work their wayin. Nothing in the 
shape of haustoria could be observed, but the appearances are 
distinctly suggestive of parasitism, if serious local damage to the 
host is any indication. The outermost small-celled layer has 
frequently disappeared, and the young plug, or branch from an 
older one, is clearly seen penetrating between the individual cells 
of the host, the contents of which show large morbid granules, 
or oily-looking drops, accompanied by general disorganization, 
whilst walls in all stages of breaking down (absorption ?) are 
frequent. Here again the question of the modus operandi has to 
be considered. In this case there is a much stronger suggestion of 
enzymic action than in the outward passage of the endogenously 
developed filiform thallus. All the appearances in the neighbour- 
hood of these organs of attachment are suggestive of the secretion 
of some solvent medium by the cells of the penetrating branches. 
Moreover, it is more probable that in this case there is a 
nutritive digestion, as the innermost articulations of the creeping 
thallus lose their pigment as the thallus increases in thickness 
and thus cease to be self-sustaining, so to speak, and become 
either entirely dependent on the more superficial assimilating 
articulations, or partially on these and partially on the host. 
It is quite possible, however, that these plugs serve simply as 
hold-fasts, and that their disintegrating power is correlated to 
that function only. The above observations suggest a profitable 
