(leony: \) 
such different habits of life. The purpose of those adaptations 
was perfectly obvious, as he felt certain every Fellow present 
would admit. He had confidence, therefore, in stating that 
the Prisopi, so far as their habits were concerned, were not 
at all exceptional, but were just like all the other members of 
the same family, the habits of which were well known and 
well understood. From this he was led to offer some remarks 
about another genus of Phasmidae which had an interest of 
the same kind. The genus Cotylosoma has on each side of the 
metathorax a row of five remarkable leaf-like structures ; and 
Wood-Mason, the author of the genus, had no hesitation in 
describing these as tracheal gills. Dr. Sharp and Mr. Water- 
house had questioned this interpretation of the structures. 
He had himself recently examined them; and finding the 
presence in them of numerous pigment spots, and the complete 
absence of tracheae, he was quite convinced that they were 
not tracheal gills. They were, however, structures of a peculiar 
and very interesting character, for which it was difficult to 
find anything quite analogous in other families of insects; but 
he believed their function was merely procryptic, and that 
they were developed in harmony with other features, to effect 
the concealment of the insect from its enemies. They were 
movable, and, looking like diminutive wings, suggested a 
possible explanation of the use to which the primitive wings 
were first put in the terrestrial ancestors of the winged insects. 
That Cotylosoma had the habits of other Phasmidae was clearly 
enough shown by the account MacGillivray had given of 
C’. carlottae, a species very closely related to the one described 
by Wood-Mason. He states that “it was said to be found on 
the trunks of trees,” exactly what we should be led to expect 
from the description he had given of the colours of the insect— 
colours that “altogether reminded him of some kinds of 
lichens,” His description of this species, under the name of 
Prisopus carlottae, although published several years before the 
papers written by Murray and Wood-Mason, was evidently 
not seen by either of them; nor had they the advantage of 
seeing fresh specimens in which the original colours of the 
insects were still retained. Had they been so fortunate as to 
have seen a specimen like the one passed round that evening, 
