Antarctic Meltwater Pools — Thomas 
517 
He believes there is a marked stratification of 
salinity due to meltwater in the upper layers. 
The present author observed that nearly all 
pools are subject to contamination in some de- 
gree by spray when sea ice is absent. Pool 6 
(S %o 24.3) is periodically invaded by sea 
water. Pools 2, 9, and 11 are continually flushed 
during ablation of the snow field. The presence 
of fresh water forms in pool 6 may be accounted 
for by stratification, in which meltwater occu- 
pies the upper layers, and by migration of biota 
from a higher pool. 
That lower forms of life can be frozen into 
ice and revived upon thawing has been ob- 
served by several authors. Kapterev (1936) 
found that Cyclops and Planorbis survive after 
being thawed out of shallow pools near the 
Amur River. He observed 20 genera of extant 
algae and a crustacean revived after being 
thawed from permafrost, in which he estimates 
they might have been frozen a thousand years. 
Luyet and Gehenio (1940) include tardigrades, 
rotifers, paramecia, euglenids, amoebae, and 
diatoms with organisms which survive extreme 
cold. 
The present author obtained, simultaneously, 
three samples from a pool in Massachusetts, 
the surface of which was frozen. One sample 
was not frozen. A second was frozen solid under 
natural conditions for a week. The third was 
frozen into solid ice in less than two hours and 
maintained at -15° C in total darkness for a 
month. When the two frozen samples were 
thawed no mortality was apparent. The follow- 
ing organisms were found in the three samples: 
Rhizoclonium cladophora, Melosira variens , 
Fragilaria sp., Tabellaria sp., Navicula sp. A 
and B, Rophaloidia sp., Amphora sp., Epithe- 
mia sp., Chilamonas paramecium, Urostyla sp., 
Tintinnopsis sp., Paramecium sp., Chaetogaster 
sp., B del] old rotifers (four genera). 
According to Scholander et ah (1955) a 
great many aquatic plants and animals (includ- 
ing Daphnia ) spend the winter frozen into the 
ice of lakes and pools in the Arctic. Similar 
observations have been made by others. 
Luyet and Gehenio (supra cit.) examined 
causes of death of organisms due to freezing 
as postulated by several authors. They conclude, 
"How enormous hydrostatic pressures have no 
action on protoplasm while pricking on a glass 
needle may, in some instances, start coagula- 
tion is entirely unknown.” In the nineteenth 
century, bursting of cells by ice formation was 
widely believed to cause death. 
According to Plateau (1872), ". . . it is a 
known physical principle that the cavities in 
a solid body expand like the body itself. There- 
fore, the cell contents cannot be crushed by 
freezing.” He illustrated this observation with 
an apparatus consisting of a glass tube on the 
end of which was a rubber bulb filled with 
a liquid, and immersed vertically, the open end 
up, in a flask containing water. When the lat- 
ter froze in the flask, the leevl of the fluid in 
the tube remained unchanged. This indicated 
that no pressure was exerted on the rubber 
bulb. Luyet and Gehenio take issue with Plateau 
on the grounds that (according to them) the 
results of his experiment disagreed with the 
principle he sought to invoke. "He should have 
observed a lowering of the level of the fluid in 
the manornetric tube if the cavity around, the 
tube were expanding.” 
But Plateau was right. Ice seamen are famil- 
iar with this principle. A thin-skinned ship 
may be frozen into static ice without damage 
(Dieck, 1885). For several years, the gasoline 
tankers (YOGs) were frozen annually into the 
ice in Arrival Bay, Antarctica. While the cav- 
ity created by the ship expands, new ice forms 
at the same rate between the ice-body and the 
vessel’s hull. Hence, an animal frozen into ice 
becomes an integral part of the system without 
being subject to pressure. 
The experiments of Scholander et al. (supra 
cit.) and of Kanwisher (1955) show that re- 
sistance to cellular freezing runs parallel with 
the ability of an organism to withstand dehy- 
dration. From the observations of Becquerel 
(1936) it appears that, in general, the lower 
forms enjoy this ability to a greater extent than 
do the higher ones. 
The rotifers and some other animals in Table 
2 were identified by Dr. C. R. Russell of Can- 
terbury University, Christchurch, New Zealand. 
He says (personal correspondence) the rotifers 
Brachionus quadridentatus and B. calcyciflorus 
are generally found in temperate waters and 
the lowest temperature in which these species 
