PROCEEDINGS OF SCIENTIFIC SOCIETIES. 151 
arrived at what, on good grounds, he assumes to be important results 
respecting their life-history. He states that the remarkable power of 
darting each mandible separately with speed and accuracy of aim far in 
advance of the body, the powerful retractile muscles attached to these 
mandibles, the organization of the remainder of the mouth, the extreme 
swiftness of the creatures, the use of the front legs as tactile organs only, 
and not for the purposes of locomotion, and the ample supply of tactile 
hairs in front only, seem to fit the animals for a predatory life, and point 
to habits similar to those of Cheyletus and Trombidium, rather than to those 
of the true vegetable feeders, such as the Oribatide and Tetramachi. He 
further concludes :—(1) That Megnin is correct in saying Gamasus cole- 
optratorum, and other allied creatures, with the conspicuously divided 
dorsal plates, are not species at all, but immature stages of other 
species. (2) That the division of the dorsal plate is, in most cases at 
all events, a question of degree, and does not form a sound basis for 
classification, as applied by Koch, Kramer, and others. (3) That the 
dorsal plates do not grow gradually, but alter in size, shape, or development 
at the ecdysis. (4) That Megnin is right in saying that the characteristic 
of the so-called G. marginatus is simply a provision possessed by the females 
of a large number of species. (5) That the extent of the white margin 
depends upon the extent to which the abdomen is distended by eggs. 
(6) That Megnin is in error in saying that coleoptratorum is the nymph 
of crassipes. The nymph of crassipes does not show any divided dorsal 
plates which can be seen on the living creature. (7) That in the species 
which I have bred there is not any inert stage before the transformation or 
ecdysis. (8) That in the same species it is the adult female, and not the 
immature one, as Megnin contends, which breeds. 
February 17, 1881.—Franx Crisp, Esq., LL.B., F.L.S., in the chair. 
Mr. A. Hammond exhibited a specimen under the microscope, along 
with a drawing of a portion of the wall, of the socalled glandular sac of 
the larva of the Puss Moth, Cerura vinula, from which that insect is said 
to eject an acid liquid when alarmed or irritated. He stated that although 
there could be no doubt that the organ was the source of the excretion 
in question, there nevertheless was some difficulty in regarding it as a true 
glandular structure from the large quantity of chitinous matter constituting 
the wall of the sac itself. 
Dr. Francis Day read a paper “ Observations on some British Fishes.” 
He pointed out that Pimelepterus cornubiensis, Cornish, is identical with the 
American Pammelas perciformis, Mitchell; that great confusion exists in 
the works of Yarrell and Couch respecting the Tunnies and their allies, 
most if not all the examples of the Short-finned Tunnies being in reality 
specimens of Pelamys sarda; that the Comber Wrasse (Labrus Donovani, 
