Notes. 
173 
following list of species on which they have been observed:— 
V. racemosa , dichotoma , clavata , caespitosa, geminata, uncinata, 
terrestris. Lister has also observed them on V aversa , Hass, and 
V. Dillwyni , Ag. The animal (rotifer) which gives rise to them is 
described in the earlier papers as Cyclops lupula , Mull. ; but Balbiani 
and others have identified it, in all the species examined, with Notom- 
mata Werneckii , Ehrb. 
I append a figure (Fig. 5, x 200) of one of these ‘ galls ’ found on 
a Vaucheria growing on the surface of a wet rock at Buckfastleigh, 
Devon, in August 1889. Having no organs of 
fructification, the species could not be determined 
with certainty, but is probably V. sessihs, Vauch. 
The ‘gall’ is a vesicular appendage attached to 
the filament nearly at right angles ; its length 
from five to six times, and its greatest breadth 
about twice that of the filament, from which it 
springs by an open neck about as wide as the 
filament. The protoplasmic contents of the 
filament and of the vesicle are in complete 
communication ; and the latter is rich in chloro- 
phyll, which however has retreated from the cell- 
wall, leaving a parietal space filled with granular 
colourless protoplasm. Within the chlorophyllous 
portion is seen the living animal, which feeds Fig. 5. 
upon the protoplasm of the vesicle, but, according 
to Balbiani, not on the chlorophyll. 
The ‘ galls ' are described by several observers as frequently present 
in large numbers on the same filament ; but they are certainly some- 
times solitary. From the fact that the filaments attacked are never 
fertile, it has been suggested that they weaken the plant, and prevent 
its forming sexual organs ; but Balbiani has clearly shown that the 
‘ gall’ is a lateral fertile branch which the parasite has entered at an early 
stage, prevented it from forming oogones and antherids, and cause 
it to swell to from four to five times its original size by hypertrophy, 
brought about probably by the action of a stimulating secretion, as in 
true galls. This is further confirmed by the horn-like protuberances 
with which they are frequently furnished ; but these were not present 
in those observed by me. If this view of their formation is correct, 
they are not accurately described as galls— a term which should be 
