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SECTIONAL TRANSACTIONS.—D. 421 
Polychet is associated with drastic changes in the shape and size of the 
spicules forming the tunnel. The question arises whether other environmental 
peculiarities may not result in ‘ Modification Species’ in many corners of the 
animal kingdom. 
6. Prof. J. Arruur THomson.—A Long-lost Aleyonarian. 
In 1882 G. von Koch briefly described from near Naples Gorgonella bianci, 
n.sp. His note was compressed into a few lines. In his famous Naples Mono- 
graph (1887) he remarked that he had not seen it again. A few years ago a 
specimen (dated 1879) was received from Naples which corresponded entirely 
with the notes made by von Koch, and showed that he was right in establish- 
ing a new species. It is quite distinct from other Mediterranean Gorgonids 
and deserves more complete diagnosis. Its name should be Leptogorgia bianci, 
von Koch. 
7, Prof. J. Cossar Ewart, F.R.S.—The Structure, Development, 
and Origin of Feathers. 
It has been asserted that if we assume birds are descended from reptilian 
ancestors, we may assume feathers are modified scales. Evidence of the descent 
of birds from reptiles we have in Archwopteryx, but the geological record affords 
no evidence in support of the assumption that feathers are modified scales. 
Our only chance, in the absence of fossils, of ascertaining how feathers were 
evolved is by studying the nestling feathers (prepenne) which precede the true 
feathers (penne). This study suggests (1) that feathers were not originally 
acquired to enable birds to fly, but to prevent the loss of heat; (2) that when 
birds were in the making the coat consisted for a time of simple umbels, like 
those forming the first (protoptile) coat of penguins; (3) that when a cold, dry 
period was succeeded by a cold, wet period the original downy coat was 
succeeded by a fur-like coat like the second (mesoptile) plumage of penguins ; 
(4) that in most modern birds this second (mesoptile) coat has been completely, 
or all but completely, suppressed; (5) that feathers, like hairs, were formed, 
not out of scales, hut out of the skin lying under and between scales. 
Believers in the scale origin of feathers have hitherto assumed that a perfect 
true feather consists of a single shaft or blade—that, ¢.g., the long after- 
shaft of the emu feather is a secondarily acquired feature. he developing 
feathers of the emu, grouse, and many other birds conclusively prove, however, 
that complete true feathers (yennc), like true down feathers (plumule), consist 
of two shafts which are practically alike in origin and structure. 
Friday, September 9. 
8. Prof. D. M. 8S. Watson.—Dry Land and the Origin of the Bony 
Vertebrates. 
The bony vertebrates differ from all others in the presence in all of a lung or 
air bladder, and in the Dipnoi, Amphibia, and Polypterus of larval external gills. 
The air bladder is clearly homologous with the lung. It is actually used as a 
lung in the relatively primitive Polypterus, Lepidosteus, and Amia. It is not 
possible to conceive of its origin primarily as a hydrostatic organ. Hence it 
arose as a lung. A marine fish has no obvious need of accessory respiratory 
organs of the type of a lung if it lives a normal life; therefore the lung pre- 
sumably arose in a fresh-water fish. The conclusion of Joseph Barrell that it 
develops first in fish living in the intermittently running streams of an arid 
district with seasonal rainfall is adopted. It hence follows that all known bony 
fishes are derived originally from fresh-water forms. External gills do not 
occur in larval Neoceratodus, whose eggs are laid separately amongst the 
Valisneria in large deep pools where the aeration is comparatively good. They 
do occur in Lepidosiren and Protopterus, which lay large masses of eggs in 
small definite nests where the conditions of aeration are shown to be very bad 
by the development of functional external gills by teleost larve. It is hence 
natural to believe that external gills first arose under the same conditions as 
lungs in fish which remained under these conditions after the Actinopterygii 
had left them for more normal regions. The external gills may have been 
originally developed for the purpose for which they are actually used by 
