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in constructing the case, as though the little beings understood the neces- 
sity for resisting the force of the water. They are somewhat fastidious, 
and prefer uncooked meat. When turned out of their cases, air-bubbles 
appear on the surface of their bodies, which in a rapid current cause them 
to float to the surface, when they die from exhaustion. “ The caddises 
are so excessively pugnacious, that I am always obliged to keep each in a 
separate vessel. If that precaution were not taken, instead of peaceably 
constructing their houses, a fierce warfare would be carried on between 
them which would result in the death of the weakest party.” 
The Emigration of the Lemming . — The cause of the emigration of this 
animal ( Lemmus norvegicus ) has for a long while engaged the attention of 
naturalists. M. Guy on, in a note in the Comptes Rendus for the 7th of 
September, examines the following reasons of the periodic departures of 
the lemming : — ■ 
1 . A severe winter , which the animal has a presentiment of. — If this were 
the case, the emigration would always take place on the approach of winter, 
but this year it took place in spring. 
2. The want or scarcity of food in the localities where it lives. — The 
lemming feeds on lichens and mosses, and these were as abundant this year 
as on former occasions. 
3. The increased multiplication of the animal in certain years. — This 
appears to be the most plausible reason, and may be adopted, till some 
better explanation turns up. The lemming always pursues a right line in 
its migrations, and neither rivers nor mountains oppose its progress. It 
swims across the rivers, and either ascends or goes around the mountains. 
But, doubtless, on this point there has been a good deal of the marvellous 
mixed up with the accurate. Most probably the direction depends upon 
the fall of the ground, so that the lemmings descend like water, from the 
mountains. In their descent, they meet at the base, and travel in serried 
columns through the country, their lines diminishing as they march 
onwards, ow r ing to the influence of disease, and to the fact that various 
animals prey upon them. M. Guyon succeeded in bringing two (for the 
first time) to France. 
Two Species of Entomostracce new to Britain. — The Rev. A. M. Norman 
has lately added two new species of the genus Acantholeberis to our fauna. 
These animals have been already described by Leydig, Fischer, Muller, 
&c., but were never before observed in this country. A. curvirostris is 
remarkable for the peculiar uprightness of its head, and A. sordida for its 
deep blood-red colour. Both have been minutely described and figured 
in an important paper in the Proceedings of the Tyneside Naturalists ’ Club, 
vol. vi. part i. 
Fleas Inhabiting the Sea-shore. — These insects have been observed in 
large numbers at the sea-side by Mr. T. J. Bold. It is surprising that 
animals which are so peculiarly suctorial and parasitic should be discovered 
in such localities, but Mr. Bold assures us that he has seen them “ dancing 
about quite merrily between Hartley and Whitly, and at other times 
they have been noticed quite frequently from South Shields to Marsden.” 
— Ibid. 
The Ailanthus Silk-moth. — The Ailanthus glandulosa , or false varnish- 
