296 NATURAL SCIENCE [November 
this inspection might well, we should suggest, be assumed by the 
various Sea Fisheries Committees around the coast. 
THE METHOD OF FEEDING OF H#ZLIX HORTENSIS 
Mr E. Ratuay publishes an interesting article on the method of 
feeding of Helix hortensis, in the third part of Vol. viii. of the 
Zeuschrift fiir Planzenkrankheiten. 
' The author had noticed on the smooth bark of ash-trees certain 
undulating patterns, in the immediate neighbourhood of which, or 
at their extremities, were individuals of Helix hortensis. Myr Rathay 
therefore felt that the patterns must be accounted for by the snail’s 
method of feeding. 
To make certain of the fact, he took some bits of ash-bark on 
which no patterns had been traced, set them in an upright position 
so as to keep them fresh in the water, put a Helix on each, and 
covered them over with a glass bell. The very next day, these bits 
of bark showed traces of undulating patterns. 
In consequence of this experiment, the author’s attention was 
drawn to other smooth-barked trees, and he recognised the same 
patterns on Salia caprea L., S. amygdalina L., Alnus incana C., &e. 
These traces were noticed on the trunks to the height of 7 to 
9 metres, and the snail that was observed to be at work, produced 
them by slowly advancing his body and swaying his head alterna- 
tively to right and left. 
One might suppose that the gasteropod fed himself thus by 
gnawing the bark of the tree, but it is nothing of the kind; he 
attacks the spots where the bark is powdered with a small alga, 
Pleurococcus vulgaris, Menegh., and scarcely touches the outer skin 
of the bark. 
In fact, in the excrement of Helix hortensis are found the cells 
of Plewrococcus almost intact. 
In accordance with the experiments detailed in the note and 
after the employment of various appropriate reagents, it 1s recog- 
nised, not only by microscopic examination, but by chemical experi- 
ment, that the cells of Plewrococcus have been evacuated intact with 
their chlorophyl. 
The author’s conclusions are as follows :— 
1. It is only on smooth barks sufficiently coated with alga that 
the undulating patterns can be detected. 
2. It can easily be observed, especially on the older trees, that 
Helix hortensis does not eat the outer skin of the bark and scarcely 
touches it. 
3. The excrement of the same gasteropod, taken a great height 
up the tree, is chiefly composed of cells of Plewrococeus with 
very few fragments of peridermis. The extraordinary thing about 
