ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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and rising again. The simple experiment of adding some fresh water 
to a vessel containing floating Sphasrozoa is effective, for they sink at 
once ; that this is not the result of a fatal shock may be proved by rapidly 
transferring some of those which have sunk to normal sea-water again, — 
where they float as before. 
An average of measurements shows that a floating colony consists of 
vacuolar fluid to about two-thirds, of gelatinous substance to about one- 
third, while the small remainder is plasma. To keep this plasma up, 
the hydrostatic part (vacuolar and gelatinous) need only have a specific 
gravity *00002 less than that of sea-water. It is not less at any rate 
than 1-026, while that of sea-water is 1*028. In some cases the jelly 
has a greater specific gravity than the water, and then the floating 
depends on the vacuoles. 
Brandt reaches the interesting result that the carbonic acid gas 
formed in the organism is dissolved in the vacuolar fluid, and that 
according to the laws of osmosis this brings about a lessening of the 
salt-content and thus of the specific gravity. 
A disappearance of vacuoles causes sinking, their reappearance rising. 
The sinking may be due to mechanical stimuli which cause retraction of 
pseudopodia, but this seldom lasts long unless sufficiently violent to 
be fatal ; or to thermal stimuli which have a longer effect. In no case 
was spontaneous sinking observed, unless the sinking associated with 
spore-formation be ranked as such. 
Nuclear Division in Collozoum.* — Prof. P. Mitrophanow has studied 
the division of the nuclei in the vegetative phase of Collozoum inerme. 
In spite of all the apparent simplicity of the process of division, it is 
really indirect, though simplified. Future observations will show 
whether the case illustrates a primitive form of karyokinesis, or an 
adaptation to special physiological conditions. 
New Pliocene Foraminifera.| — Sig. G. A. De Amicis describes some 
new forms from Pliocene deposits in Sicily : — Nodosaria Di Stephani, 
N. Ciofali , Lingulinojjsis Jiimerensis and Uvigerina canariensis d’Orb. 
forma distoma n. 
Evolution of the Corpuscles in Silkworm’s Eggs4 — It is well 
known, says M. E. Duclaux, that pebrine parasites in silkworm’s eggs 
remain in a quiescent condition from the time the eggs are laid by the 
moth until the period of hatching arrives. Active development is first 
evident when the tissues of the embryo are beginning to form owing to 
incubation in the following spring. Why should there be this coinci- 
dence between the evolution of the embryo and that of the corpmscle ? 
Does the latter also require a winter’s slumber, or is the egg an un- 
suitable medium and only utilisable when the embryo has been formed, 
owing to the changes which have occurred in the substance of which it 
is composed ? To learn something about the conditions it is necessary 
to induce premature hatching of the eggs, and for this purpose several 
means can be employed, the action of cold, acids, friction, and electricity. 
Choosing the last the author found that if in the silkworm’s egg the 
* Arch. Zool. Exper., iii. (1895) pp. 623-7 (1 pi.), 
t Atti Soc. Tosc. Sci. Nat., xiv. (1895) pp. 18-31 (1 pi.), 
t Ann. Inst. Pasteur, ix. (1895) pp. 885-91. 
