1898] NOTES AND COMMENTS 297 
this is that these cells are evacuated apparently intact, not only 
with their chlorophyl, but with the other substances that they 
contain. 
4. It has been noticed that Helix hortensis produces the same 
patterns on the lattice work of a wooden fence covered with Plewro- 
coccus vulgaris. <A figure of the pattern referred to will be found 
reproduced in La Fewille des jeunes Naturalistes, September, from 
which journal we take this uote. 
ABNORMAL SHELLS OF PLANORBIS 
THE abnormalities of our fresh-water snails will be no new fact to 
bring before the notice of our readers, but attention may well be 
directed to a paper by Mr A. G. Stubbs on abnormal specimens of 
Pianorbis spirorbis from Tenby. The paper was read before the 
Conchological Society, and is published in the October number of 
their Journal. A good plate is provided, and the shells are seen to 
be contorted in every direction, but mainly into that of a spiral, 
some of these so much drawn out as to be nine or ten times the 
height of the normal shell. Mr Stubbs accepts Mr J. W. Taylor’s 
explanation as to the cause of this curious distortion :—* that when 
the water [in this ditch] is nearly dried up, the efforts of the crea- 
tures in forcing their way through the thick mud in which they are 
sometimes left partially embedded, to again reach the water, may 
easily cause an alteration in the direction of a new shell growth, if at 
the time in course of formation.” 
A REMARKABLE MARINE ORGANISM 
AMONG a number of sponges from Ramésvaran Island, Gulf of 
Manaar, sent to Dr Arthur Dendy for identification for the Madras 
Museum, were some fifteen specimens of cushion-shaped masses of a 
brown colour, from 13 mm. to 36 mm. in diameter, attached to 
rock fragments. These masses are compact and tough in texture, 
after preservation in spirit, like indiarubber, and there is a deal of 
sand in the deeper layers. When cut in half vertically they show 
strongly-marked, concentric lamellae, the effect of alternating bands 
of flocculent (opaque) and transparent layers. The opaque layers 
are connected together by a coarse network of radially ramifying 
strands. In the transparent layers are seen, after careful examina- 
tion, innumerable exceedingly slender unbranched threads, which 
prove to be the cellulose sheaths of chains of short, rod-like 
bacteria. Dr Dendy thinks that there are two possible views as to 
the nature of Pontobolbos, as he calls this remarkable structure, and 
these are (1) that the organism is entirely bacterial in origin, the 
