Juny 30, 1897. ] 
cell structure. Until quite recently investi- 
gators have been unable to find any indica- 
tion of that organization of the protoplasm 
into a nucleus and chromatophore, such as 
is present in the ordinary plant cell. Now 
botanists are able to distinguish nuclear 
matter in the cells of some of the larger 
types, but it is found in a scattered form 
with vague contours and never in the shape 
of a well-defined, compact structure. The 
phenomenon of cell division is here found 
in its simplest type and gives the name to 
this group of plants. The cell simply splits 
apart and there are two individuals where 
formerly there was one. The cells may re- 
main attached to one another and so form 
filaments of considerable length, but each 
cell is probably physiologically quite inde- 
pendent of its neighbors. The facts plainly 
indicate that the protoplasm of these types 
is not as highly organized as that of more 
complex forms of plants; probably they are 
able to withstand these unusually high 
temperatures because of this low grade of 
protoplasmic organization. Perhaps, but 
this does not necessarily follow, these or- 
ganisms resemble more closely the primi- 
tive first forms of life than any other 
living types. One would like to know 
about the precise conditions governing 
the lives of these simple cells and some- 
thing of their past history. It is possible 
that they may have crept into the hot 
springs from the colder water, or perhaps 
their ancestors may have always lived 
under the infernal conditions which now 
surround them. A very thorough study of 
various pools and streams at different tem- 
peratures might solve the problem. The 
field of study is as interesting as itis diffi- 
cult. 
Now let us examine these organisms in 
their role as geological agents or factors 
influencing the deposition and shape of the 
formation. We must remember that the 
formations are of two sorts: first, the calcium 
SCIENCE. 
153 
carbonate deposits illustrated most strik- 
ingly by the immense pile at Mammoth 
Hot Springs; and second, the silicious 
formations of the geyser basins. Calcium 
carbonate (CaCO,), the substance which 
makes up the chief part of all limestone 
and marble, of coral and most shells, is 
practically insoluble in pure water. How- 
ever, water charged with carbon dioxide 
(CO,) dissolves calcium carbonate, and it 
is pretty generally believed that the latter 
passes over to a new substance, calcium 
bi-carbonate with the formula Ca (HCO,),. 
But calcium bi-carbonate is not known in a 
solid crystalline form because, when water 
containing it in solution is allowed to stand 
exposed, the carbon dioxide escapes and 
the usual calcium carbonate immediately 
separates out from the solution. 
The water that issues from the formation 
on the terraces of Mammoth Hot Springs 
has been under pressure and is highly 
charged with carbon di-oxide. It holds an 
unusually large amount of calcium carbo- 
nate in solution, a fact for which the bed 
of Mesozoic limestone, through which the 
boiling hot water passes on its way to the 
surface, is responsible. When the water 
emerges from the orifices of the hot springs 
and spreads out in the shallow streams and 
pools there is an immediate escape of car- 
bon di-oxide from the supersaturated solu- 
tion. The insoluble calcium carbonate is 
then thrown down as the dazzling white 
deposits of travertine. One may see the 
results of this property of the hot water 
illustrated by the absurd incrusted baskets, 
pine cones and horseshoes that are on 
sale at the hotels. This phenomenon is, of 
course, in no way connected with the activ- 
ity of the organisms, and there is no ques- 
tion but that travertine would form and 
terraces would be built up even if no plant 
life were present in the water. 
But the plant life undoubtedly hastens 
the deposition of calcium carbonate in the 
