SCIENTIFIC SUMMAKY. 
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by the former naturalist are most probably the same structure as those 
which he himself has termed sarcoblasts. There is no true circulation of 
vital fluid in the Amoebae ; the appearance of one is deceptive, and results 
from mechanical causes entirely. The current of particles tends toward 
the more prominent pseudopods, and is caused by the rush of protoplasm 
in that direction ; the backward stream is only apparent, the deception 
being produced by the rushing of the outward particles past others which 
are at rest ; thus producing the same phenomena as that seen when a rail- 
way carriage is moving at a great speed. “ One series of young individuals 
seems to be derived from the conversion of each free sarcoblast into a 
polymorphous body, devoid of cilia or flagelliform organ, but provided 
from the first with a nucleus or contractile vesicle and a rudimentary 
villous organ.” Dr. Wallich supposes that another set of new beings 
may “ result from a similar conversion of each encapsuled nucleus into a 
polymorphous body, in which, besides the organs just enumerated, may 
frequently be seen two or three spherical masses undistinguishable from 
the sarcoblasts.” A third and more abundant brood may be “ derived 
from each separate granule of -the naked mulberry-like nuclear masses.” 
He thinks it would be idle to attempt an explanation of these various 
processes in the present condition of our knowledge, as the information 
required for their solution is far greater than any we now possess. 
He records having himself observed the transition from the naked to the 
testaceous condition in specimens of free Amoebae preserved in glass cells. 
And, on the authority of Mr. Tomkins, he states that the animal of 
Arcella vulgaris has been seen to evacuate its shell and move away in the 
nude condition. — Annals of Natural History , No. LXXI. 
Habits of the Caddis-Worm. — Dr. J. E. Gray communicated to the 
Zoological Society some time since, a letter which he received from Miss 
E. M. Smee in regard to the habits of these peculiar larvae. The observa- 
tions of this lady are of exceeding interest. Having been surprised that 
such creatures as water-maggots could build houses for their own recep- 
tion, she determined to discover the extent of their capabilities in this 
direction. In order to do so, she removed some specimens from their cases, 
and supplied them with materials other than those found in their habitats ; 
and the result of her experiment was, that with some materials the caddis- 
worms had made very perfect cases, but with others they were unsuccessful. 
When they were supplied with particles of an irregular outline, such as 
glass, amethyst, cairngorm, onyx, agate, coral, coralline, marble, shells, 
jet, brass-shavings, gold-leaf, silver-leaf, &c., they formed perfect cases. 
But when rounded substances, such as glass beads, were the only ones 
they could obtain, the larvae were unable to proceed with their architec- 
tural pursuits. She tried them with pine-wood, but the oily substance it 
contained stupefied the worms and suspended their operations. They also 
failed when varnished or painted particles were used. They do not affect 
all metals indiscriminately ; seeming to have a distaste for lead, copper, 
and tin. The greatest number of cases which any larva would make was 
five ; the last always being brittle and badly cemented. A material which 
was rejected by one was distasteful to all. The more rapid the current of 
water in which they live, the greater the density of the particles employed 
VOL. III. NO. X. U 
