23 
Mr. L. B. Hall, F.L.S,, gave a lecture (illustrated with 
lantern slides) on ‘‘ Adaptations in Plants.’’ The lecture dealt 
chiefly with the cecology of mosses. 
Friday, April 15th, 1904. Mr. P. Macleod Yearsley, F.R.CS., 
F.Z.S., in the chair. 
Mr. Hugh Findon read a paper entitled ‘‘How Shells 
are Built,’”’ and having shown by means of a diagram, that 
the general shape of a shell was no guide to the species of animal 
which inhabited it, he demonstrated the fact that the forms of 
all shells were founded on a hollow cone, even the multi-spiral 
Terebra and Turritella, and the bivalve Solen or razor-shell. 
Mr. Findon then expressed an opinion that the usual belief of 
some conchologists that the shell was merely a calcified portion 
of the mantle was quite incorrect, and supported his position by 
various observations on the habits of the animal and its organic 
connection with the shell. Taking, in detail, the construction of 
the shell, he first explained the character of the outer layer (or 
periostracum), this being a horny protective skin. Various speci- 
mens were shown with this covering in situ, also eroded specimens, 
which had lost this protection. The cellular layer, which directly 
underlies the periostracum, was illustrated by sections of various 
species, and Mr. Findon showed how the “ sculpturing”’ had its 
origin in the deposition of this part of the shell. The chief con- 
stituent of this and the succeeding layer being calcium carbonate, 
the most common inorganic forms of this mineral were exhibited 
for comparison. The third (or prismatic layer) was next described, 
with its most complicated structure varying in the different species, 
- the mother-of-pearl.of the pearl shells and the china-like interior 
of the porcellaneous species being fully illustrated with suitable 
specimens. The structure and the form of shells were pointed 
out, in conclusion, as being constructed to obtain the greatest 
strength with the least material. 
The following exhibits were placed upon the table :—A Flying- 
fish (Exocetus volitans) by Mr. Hugh Findon, and the gland of a 
Musk Deer by Mr. F. C. Channing, F.Z.S. - 
: Friday, May 13th, 1904. Mr. P. Macleod Yearsley in the 
chair. 
Mr. Montagu F. Hobson, F.L.S., F.E.S., read a paper on 
‘sLepidoptera: their Enemies and Means of Defence.” 
(illustrated with named specimens mounted im situ). Mr. Hopson 
stated that in all the three stages of their life, as larva, pupa and 
eee the Lepidoptera are subject to the attacks of enemies 
