178 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
enter into the division-cycle of ovarian or seminal cells must be received 
with the greatest caution ; all such statements should be re-investigated, 
and it is probable that in all cases they will be found to be without 
foundation. The view of some authors that there is no important dis- 
tinction between amitosis and mitosis is, in the present state of our 
knowledge of the processes of nuclear division, seen to be erroneous. 
Import of the Chief Nucleolus.* — Dr. Y. Hacker distinguishes the 
numerous accessory nucleoli from the single large chief nucleolus. The 
former, as seen in the germinal vesicles of many Vertebrates, are said to 
contain the products of metabolism in the chromatin ; the latter, as seen 
in Echinoderm ova for instance, is a more differentiated “ organulum ” — 
a “rhythmically pulsating organ of excretory and probably also of 
secretory (or secretion-storing) importance.” Hacker’s observations, of 
which a full accent is promised, relate chiefly to the nuclei of Cyclops , 
Cryptochilum, Canihocamptus, and the like. 
Changes induced by Urari in the Wandering Cells of the Frog.f 
— Mr. W. B. Hardy and Dr. Lim Boon Keng find that the introduction 
of urari leads to an increase in the number and in the size of the cells 
in the lymph, followed by a decrease which is greater than the increase. 
This increase is due both to immigration and to proliferation. The de- 
struction of cells is, at first, of the nature of a passive death and disso- 
lution of the cells in the plasma ; later on, cells with apparently normal 
granulation and nuclei are bodily ingested by enlarged hyaline cells. 
These latter manifest phagocytosis at an early period, and during the 
resolution of the disease they mainly destroy the eosinophile cells. 
y. General. 
Influence of Low Temperature.^— M. R. Pictet has made since 1869 
numerous experiments on the influence of extreme cold on organisms. 
Selecting forms whose normal life is well known he plunges them into 
vessels containing dry air at temperatures varying from -f- 10 to — 200° C. 
and observes the effect on the various functions. In a dog thus subjected 
to — 92° the breathing becomes more rapid, the heart-beats become more 
frequent, and for some minutes the temperature actually rises about half 
a degree. The animal becomes agitated, and though lately fed it eats 
hungrily. After forty minutes, the temperature is still about 37°, but 
within the next half-hour a sudden lowering sets in, and resuscitation is 
impossible. 
Freshwater fishes were slowly frozen at from —8° to — 15°, but all 
survived ; but a temperature below — 20° was fatal. Frogs survived 
— 28°, but most were killed by — 30° to —35°. A snake survived 
— 25°, but died at —35°. Centipedes resisted —50°, but succumbed 
at —90°. A snail escaped death at —110° to —120°, but two others 
died at the same temperature. Below — 1° the eggs of birds died, frog 
ova survived slow cooling to —60°, ant-eggs were all killed between 
zero and —5°. The eggs of silk-moths survived —40°, and this tem- 
perature seemed to free them from microbes. Rotifers and Infusorians 
* Ber. Nat. Ges. Freiburg, vii. (1893) pp. 113-6. 
f Journal of Physiology, xv. (1893) pp. 361-74 (1 pi.). 
X Arch. Sci. Phys. Nat., xxx. (1893) pp. 293-314. 
