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NATURAL HISTORY

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CHAP TEE - XLV.

NATURAL HISTORY OF THE DIATOMACE,

Vv
BY A. MEAD EDWARDS, M.D.

PREFACE.

It is desirable that the reader of the present brief sketch should, at the outset, under-
stand that it is intended to be of an essentially popular character, and by no means a
scientific treatise on the diatomacee. It has been prepared in such a manner that it
will, it is hoped, bring to the attention of others besides strictly scientific observers
one of the most beautiful groups of organisms with which the naturalist is acquainted.
To that end the language employed is as untechnical as was judged consistent with
clearness ; and when it has been found necessary to use technical terms, their meaning
has been at the same time made plain. This short preface has been intended more
specially for the scientist into whose hands this volume may come, so that he may
understand its aim and purpose, and, at the same time, not judge it as he would had
it made pretence to a position among thoroughly scientific works. At the same time
it must be understood that it has of course been made scientifically correct, so that
what it teaches concerning the diatomacee may be as nearly as possible up to date,
and consistent with the latest investigations in this field of research.

INTRODUCTION.

T is a matter which is well understood at the present day, that if the
geologist desires to carry out, in a systematic and scientific manner,
his investigations into the history of the globe upon which he dwells,
he must earnestly and conscientiously qualify himself for extended and
searching observations in many more branches of knowledge than his
predecessors of but a few years back considered necessary to the accom-

-

NATURAL HISTORY OF THE DIATOMACEA®, 417

plishment of their labors. To properly comprehend the structure and
modes of formation of strata, be they made up of solid rock or more
loosely aggregated material, he must be a mathematician of no low order.
To understand the how, the why, and the where of the great stone book
laid open to his eye, to read aright the record of the rocks, he must call
in to his assistance at least the learning of the physicist, the chemist, and
the biologist, if he be not—which, in our present and ever growing state
of knowledge is practically impossible—a physicist, a chemist, and a
biologist himself. But as it would be evidently impossible for any one
man to be thoroughly skilled in all these branches and their various
ramifications at one and the same time, the advanced and advancing
geologist of to-day carries out the following special plan, when engaged
in the study of any tract of country. He secures the codperation of a
number of specialists, persons who have devoted their time and attention
more particularly to the study of distinct sections of science, so that
the highest skill shall investigate for him the several parts of the work,
and thus individual bricks will be contributed to the edifice which
the geologist desires to erect. To this end he is aided by at least a
chemist, who analyzes for him his rocks, his metallic ores, his marls,
or his soils; a zodlogist, who studies the animals found in the section
of country gone over; and a botanist, who turns his attention to the
plants discovered in the district traversed. If he desires to carry his
investigations still further, or if the particular section of country over
which his labors extend requires that he should do so, he calls in to his
assistance individuals who have turned their attention to particular
branches of chemistry, of zodlogy, or of botany. Thus, insects may
abound in his field of work, and the farmers will like to know something
about the ravages they commit upon the crops; or, vegetable diseases
may afflict those crops; or, the rocks may be of a kind made use of in
building; or, remarkable kinds of deposits, of great interest to science or
of value in the arts, may occur. In all of these, or any similar cases, it
will be necessary that the subjects should be investigated by competent
observers, and they must be found, and their codperation secured. Where
the geology alone, as restricted by the boundaries which limited it a few
years back, is considered, but few of these specialists will be required to

assist. But, at the present day, and, more particularly, as is the case
YOR ih 55

418 PHYSICAL GEOGRAPHY.

with our state surveys, where the gentleman who accepts the position
of state geologist is expected to make his investigations practically appli-
cable and at an early date, the field of labor is very much more extended,
and the assistants required much larger in number. Hence it has come
to pass that the modern geologist recognizes the necessity of attaching
to his staff of assistants one who is specially skilled in the use of the
microscope, an instrument, the proper employment of which necessitates
a long and severe schooling of the hand and mind, but more particularly
the eye in a peculiar manner and direction. For microscopy has become
a science in itself, so that, though the naturalist, the chemist, or the
physician may possess and look through microscopes, yet it requires one
who has mastered its secrets, and has skilled himself in its most advanta-
geous workings, to apply it so as to obtain the best results. But, even in
microscopy as a branch of science, there are specialists. Thus, we find
one who devotes himself almost exclusively to perfecting the optical por-
tions of the instrument; another will study its application to chemistry
and toxicology alone; another, its use in medicine, pathology, and physi-
ology; another, its employment as an adjunct to geology, and so on, as
can be readily understood; for science and knowledge are growing so
rapidly nowadays that division of labor becomes as necessary therein as
it has been found to be in the mechanic arts.

These few words, by way of an introduction, have been deemed neces-
sary, so that the general reader, into whose hands these volumes may
come, might understand that the geological survey of New Hampshire
has been the first of our state surveys which has possessed a special
microscopist, a person who has turned his attention particularly to the
study of the application of that instrument, aided by other means of
research, to the investigation of geology. It is true that similar investi-
gations have been made to some extent, by others as well as himself, for
other surveys; but in no case hitherto have special collections been made
systematically, and in such a manner that any very valuable results have
been arrived at, for, in this branch of science as well as in others, a defi-
nite end should be had in view, and the specimens collected and the
examinations made be for that end. It has remained for the state of
New Hampshire to be the first to inaugurate a thorough microscopical
survey of its geology and assistant branches of science,—paleontology,

NATURAL HISTORY OF THE DIATOMACE. 419

petrology, and biology; and it is to be hoped that the results will be,
therefore, proportionally valuable and interesting to science at large, and
conducive to the welfare more particularly of the citizens of that state.
It has been considered desirable, and, in fact, necessary to the proper
understanding of the subject, that that portion of the work of the survey
which comes within the province of the microscopist should be treated of
under more than one head. Thus, at the present time, that part of his
investigations which has a particular bearing upon paleontology, or the
study of the remains of organized beings found stored up in the form
of what are known as fossils in the various strata of the earth, will be
treated of, while micro-petrology, or the examination of the minute struc-
ture of rock-masses by means of the microscope, will be considered at
another time and by another hand, as the bearings of the two branches
are so very different. The minor applications of the microscope to the
subjects coming under the consideration of the survey will be gone into
as opportunity offers and desirability requires. As it is to the study of
the remains of the minute forms of extinct beings that micro-paleon-
tology is at the present time particularly devoted, the structure of more
highly organized beings not having been investigated in this connection
to any very great extent, those smaller organisms, their life, history,
habits, and relations to geology and the useful arts, will be herein con-
sidered; and we shall begin with a group of organisms whose remains
constitute, in some parts of the world, strata of many feet in thickness,
underlying cities, and, at other points, make up the greater part of vast
mountain chains, and which have in former times played a very impor-
tant part in the history of our globe. These are the Diatomacee.

Poe oF Lake bs
A SKETCH OF THE NATURAL History OF THE DIATOMACE.

As a large majority of the persons into whose hands the present vol-
ume will come are ignorant of the characteristics of the group of organ-
isms which it is intended to consider, that is to say, the Diatomacee,
and as they occupy an important position in the scheme of the geologist,
before going into their bearings on paleontology it has been thought

420 PHYSICAL GEOGRAPHY.

best, at the outset, to devote a few pages to a sketch of their nat-
ural history, presenting familiar and readily understood descriptions of
their forms illustrated by figures, their habits, modes of growth and
reproduction, and manner of occurrence in nature, so that the value of
a knowledge of them may be comprehended, and the reader be able, if
he desire so to do, to follow up their study and learn where they are to
be found, and how they may be collected, prepared, and examined.

It is a remarkable fact that these beautiful and wonderful atomies, the
diatomacez, are so little known to biologists in general, who, we find,
have neglected in a remarkable manner to make themselves acquainted
with the so-called lower forms of life, confining to a great extent their
investigations to a study of the larger groups. This doubtless has arisen
mainly from the fact that they cannot generally be seen and much less
studied by the unassisted eye, but require, for the full elucidation of their
anatomy and physiology, the most perfect appliances of modern skill, as
epitomized in the achromatic compound microscope. Now, however,
that the microscope is coming into more general use among scientific
observers, it is to be hoped that some obscure points relating to this
group of organisms, more particularly connected with their mode of
reproduction, as well as the subjects of evolution, abiogenesis, and classi-
fication, which, it is considered, may be more thoroughly studied in
these apparently simple forms than in the more complexly organized
forms of existence, will be elucidated, or, at all events, have considerable
light thrown upon them. Unfortunately, perhaps, the forms of the di-
atomacez are so beautiful and attractive, that, as they have been in the
manner mentioned neglected by accomplished biologists, they have been
collected, observed, figured, and described by totally incompetent per-
sons, who, in very few cases, have possessed the training which would
qualify them for undertaking the investigation of organisms of which so
little is known, and whose position in the plan of being even is not
thoroughly established. Hence, a great deal of that which has been pub-
lished on this subject is totally useless, if it be not in many cases
absolutely harmful, tending to confuse rather than simplify matters,
and render the little that is known concerning their life-history obscure.
The natural consequence has been that students of the diatomacez
have fallen somewhat into disrepute, and, in some cases, observers have

NATURAL HISTORY OF THE DIATOMACEE. 421

been frightened away from a field of inquiry which was beset with
so many difficulties at the outset. Under these circumstances it is
hoped that the present sketch will recommend itself for perusal to every
one interested in natural history, and at the same time introduce to many
unacquainted with them an extremely attractive group of wonderfully
constituted and beautifully sculptured beings. Those wishing to follow
the subject up more thoroughly will find, in the works of Kiitzing, Smith,
Rabenborst, Ralfs, and others,—a list of which will be given hereafter,—
ample opportunities for making themselves acquainted with what is
known concerning the diatomacez.

The Diatomacez, or, as they have come to be familiarly termed by
those more or less acquainted with them, the Diatoms, have been so
named from a genus called Déatoma, which received its name at a time
when it was considered to be an animal, and was placed in a group to
which a celebrated German naturalist, named Ehrenberg, gave the dis-
tinctive title of Polygastrica, or, polygastric animalcules, or, minute
animals possessing many stomachs. The name WDzatoma had been
bestowed upon the organism in question from two Greek words, da,
through, and Zemmno, to cut asunder, on account of its appearing as a
number of minute, oblong boxes, attached, corner to corner, in such a
manner as to form a zig-zag chain, and looking as if the chain had been
formed from a ribbon-like band, partially broken across at intervals.
After a while, when it came to be known that the group to which the
name of polygastrica had been given was made up of many totally dis-
tinct groups,—some animals, some plants, and some neither one nor the
other, but merely broken pieces of animals, plants, or minerals,—different
forms were, one after the other, or, in some cases, many together,
removed from this heterogeneous assemblage. Some, it was found, could
be placed in divisions already known, but others had to be made into
classes by themselves, and these newly constituted groups had to have
bestowed upon them, as a natural consequence, appellations by means
of which they might be distinguished and known. The Dzatomacee was
one of these apparently natural groups, and as all the forms, it was found,
grew after a manner the same as the organism upon which the name of
Diatoma had been bestowed, that is to say, by a partial or total splitting
across, the distinctive name of Diatomacee was given to them, and they

422 PHYSICAL GEOGRAPHY.

were erected into a family by themselves, and provisionally placed in the
animal kingdom. Very soon, however, it was observed that they pos-
sessed characters inconsistent with animals as then known, but more
nearly allied to plants. For this reason they were soon removed to the
vegetable kingdom, and, after a time, ranked as alga, or water-plants
which do not produce evident flowers. Yet there have been, and in fact
still are, observers who think that these organisms were improperly
removed from amongst the animals, and the consequence has been that,
for a few years, they vacillated between these two kingdoms. By far the
greater number of naturalists, however, have come to consider them as
plants, and so they have rested up to a very late date. It has been within
the last six or eight years that their true position has apparently been
determined by a German naturalist named Haeckel, who considers that
they possess characteristics which qualify them for a position, along with
a few other minute forms of life, in a group separated alike from animals
and vegetables, and to which he has given the name of Protista. With-
out, at the present time (for it would be out of place in a publication of
the character of the present), going into the consideration of the reasons
which have influenced the eminent German naturalist in his conclusions,
suffice it that the author of this sketch coincides with him in his opinion,
and considers the diatomacez to be neither animals nor plants, but
Protista.

The diatomacez are inhabitants of both fresh and salt water, as well
as that which is brackish by reason of its being subjected to the periodi-
cal influx of the water of the ocean, or that from springs and streams.
They live in many cases attached to submerged objects, such as plants,
rocks, or wood-work ; but some species appear to be free, and unattached
to anything. It is, however, likely, as has been shown by the present
writer, that all of them spend a portion of their lives attached to sub-
stances below the surface of the water, whilst they have periods of free-
dom when they swim about, and in this way disseminate the species.
Although we find them inhabiting both fresh and salt water, yet it would
seem that there are certain forms which will not thrive in both of
them. Thus, we find certain well marked species which would seem to
be confined to the ocean, whilst others are only to be seen in running
fresh water, and still others exist solely in quiet lakes. However, so little

NATURAL HISTORY OF THE DIATOMACE. 423

has been done towards studying the local peculiarities influencing the
distribution of these organisms, that we will dismiss the subject with this
brief mention, merely pointing out that therein lies a field for investiga-
tion which will yield abundant fruit to the patient and conscientious
student.

They are to be found in all permanent collections of water, but have
never been observed in pools formed by the rain and liable to be dried
up, and they may be looked for at all seasons, although, as might have
been supposed, they appear in greatest numbers in spring and during the
autumn. The hottest days of summer, at least in such localities as the
present writer has examined, seem to be unfavorable to their growth
(that is to say, in fresh water), but they have been gathered in midwinter
from beneath the ice in the Hudson river, New York. In the ocean we
find that season affects the diatomacez, as it does most organisms which,
like them, live near tide levels; that is, they diminish in numbers as the
cold of winter approaches, only to increase again in spring.

The structure of the diatomacez is very peculiar; and althought heir
general outline can, without any very great difficulty, be made out by
using a magnifying glass of moderate power, their ultimate anatomy is
extremely difficult of elucidation, as will be exemplified further on. This
can be readily understood when we know that the largest of them are not
over eight thousandths of an inch in diameter, and that many, and those
by no means the smallest, are only two ten-thousandths of an inch across.
If the diatomacez possess an outer membrane, integument, or, we might
almost say, skin, it is extremely delicate, so much so that it has not with
certainty been detected as yet, although one or two observers think they
have seen something that looks like such a seemingly necessary limiting
portion of the individual. But we shall see hereafter that there are
organisms very closely related to those we are now considering, which
certainly do not possess limiting membranes, but whose whole substance
is homogeneous, and made up of but one kind of substance of a semi-
gelatinous consistence, and known to naturalists as protoplasm, meaning
the simplest of all living matter. It is likely, then, that the diatomacez
have for an essential base to their bodies this protoplasm ; and, reasoning
from what we know of allied organisms, it is within and from, in part,
the substance of this protoplasm that the other portions of the individual

424 PHYSICAL GEOGRAPHY.

are elaborated, constructed, and built up. What appears to be the ex-
terior membrane of a diatom is siliceous; that is to say, it is composed
of the substance known commonly as silex, but called by the chemist
silica. This is the same material as that which, crystallized, we find in
rock crystal or quartz, and which, variously colored, constitutes flint,
agate, jasper, amethyst, and various other minerals often used for orna-
mental purposes. Of course, this portion of the diatom is very hard,
and on this account what we may with considerable propriety call the
skeletons of dead individuals are used for the purpose of polishing
metals, and similar substances, under the name of tripoli—although it
by no means follows that all tripoli is made up of dead diatom skeletons.

The typical form of a mature and perfect individual diatom is con-
structed after the following manner: The outer wall, consisting, as has
just been said, of silica, is formed of two portions so fashioned that when
these are united, as they are during the life of the organism, they form
a little box, within which is enclosed the softer parts which go to make
up what have been called the “cell contents,” under the supposition that
the diatomaceze were “unicellular” organisms. Now that the old theory
of cell organization has been very materially modified, this appellation
had better be discarded, as it has been used (and in fact was constructed)
for the purpose of describing a condition, of the existence of which
there are considerable doubts. The whole diatomacezous individual has
been called the frustu/e, and under this designation we will speak of it
here. Within the siliceous wall some observers have thought that they
have detected a delicate membrane surrounding the rest of the contents,
but it is doubtful if such a limiting membrane really exists; and, in fact,
it is much more probable that the general mass of the contents is made
up of protoplasmic substance, consisting, like such protoplasm usually,
of a more or less semi-fluid material, without any differentiation of its
parts from the centre to the exterior. Enclosed within the mass of this
clear, colorless protoplasm are seen irregularly formed masses of a sub-
stance of a greater consistence, and of a peculiar light yellowish-brown
tint: this is known as the exdochrome. Sometimes the endochrome
occurs in the form of two masses, but often there are many such masses,
In either case, as a common thing, the particles of endochrome are so
disposed as to lie near to the two portions of the siliceous wall which

NATURAL HISTORY OF THE DIATOMACEZE, 425

constitute the top and bottom of the box. Besides this colored matter,
which gives the peculiar tint to the diatoms when seen in mass at certain
times, but apparently not at all periods of their existence, we find the
diatom individuals to have scattered throughout their contents, but
always within the layer of endochrome, one or more clear globules look-
ing like oil, These have been called the “oil globules,” and, when the
diatomaceze were ranked in the vegetable kingdom, were supposed to be
the representatives of the starch found in the larger plants. Ehrenberg,
who did (and, in fact, does still) rank the diatomaceze among animals, con-
sidered these clear spaces to be stomachs, and fancied he had been able
to feed these organisms on such colored matter as indigo, and see it enter
these spaces. On account of their frequently being present in numbers,
he constructed for the diatoms the name already spoken of,—Polygastrica,
or many-stomached. There is no doubt that diatomacez will absorb
indigo, or similar material, along with water, and thus their cell-contents
may become tinted; but such taking into their interior, of matter, does
not prove their animal nature, as all the Protista absorb solid nutriment,
and, in fact, many undoubted plants, under certain conditions, do the same.

The typical form of a diatomaceous individual, then, consists of a little
siliceous box with its cell-contents more or less colored of an olive-brown
tint. The variation in form of the top and bottom of the box, which are
known as the “valves,” is very great, whilst the band uniting the valves,
and called the “connecting membrane,” or “cingulum,” remains essen-
tially the same, being merely a ring, narrower or wider as the case may
be, and conforming in contour, of course, to the valve to which it is
attached, and whose outline it then typifies. In the same way, the sides
of a trunk form an oblong ring, and those of a pill-box a circular or oval
loop. Thus, in the genus Pzxnularia, the connecting membrane is
oblong, with rounded ends; in Cosctnodiscus, and the many similar
genera, circular; in 7riceratium, triangular; in Amphitetras, quadrangu-
lar, and so on, as can readily be understood, and will be made more plain
when the various forms come to be seen in their integrity. As has been
said, the outline of the valves varies very greatly, but is, for the most
part, constant in each genus. We occasionally find, however, that the
outline of the valve is the same in two or more distinct genera, which

are then separable by means of some other character. The intimate
VOL. I. 56

420 PHYSICAL GEOGRAPHY.

structure of the valve itself is very beautiful and characteristic, but we
shall be able here to consider such structure in general terms only, leav-
ing its more particular description until we note the peculiarities of a few
typical forms, which will be described in detail, and illustrated by figures
showing their outline and sculpture, as revealed by means of the micro-
scope. The minute sculpture of the diatom valve is commonly spoken
of as its “markings,” and in all cases they are generally of a similar
character on both valves. This, however, is not always the case, as we
find in some genera which pass most, if not all, of their lives attached
to objects like plants, sticks, stones, and the like, submerged in the water
(fresh, brackish, or salt) which the diatomacez inhabit. In such cases,
as they are dissimilar, and can be distinguished, it has become customary
to call that valve which is next to the object upon which it grows the
lower valve, and the opposite one the upper,—and if, as must often be the
case when the diatom is fixed to the under side of a plant leaf as it floats
upon the surface of the water, the position of the valves is reversed. In
all cases the valves are convex at the edges, although they may be some-
what flattened near the middle, so that when the edges are in contact
they enclose the cavity already spoken of, and which may be very shallow
in proportion to its width, perfectly spherical, or several times deeper
than wide.

The great point of beauty in the diatomacez, and what has attracted
to them the attention of so many unscientific possessors of microscopes,
is the symmetry and forms of these same sculpturings or markings found
upon the siliceous envelope ; and these vary in delicacy from comparatively
coarse reticulations to such extremely minute dots that no microscope
has as yet been constructed which will show us what is their true char-
acter, so that, as they lie side by side in rows, the siliceous cell-wall
appears to be marked with extremely faint lines. But this is not all, for
there are diatoms upon which even such faint lines have not been seen;
but we know that they must be fashioned after the same manner as their
brothers, and must, therefore, possess markings of yet greater fineness,
and which time, it is to be hoped, with the aid of improved means of
research, will reveal to the inquiring eye of the future observer. The
great delicacy of some of the markings found upon diatom cell-walls, and
the consequent difficulty of seeing them, has led to great rivalry in

NATURAL HISTORY OF THE DIATOMACEE. 427

makers of lenses for microscopes, and certain species have been selected
and accepted as “test objects,” by means of which the power of lenses
to show their structure has been made evident. But as this has become
a special department of microscopy we will pass it by, at the present
time, with this mere allusion. These beautiful markings are, for the
most part, hexagonal, that is to say, six-sided, or, at least, they are of
forms derived from the hexagon, that being the form most economical of
space under the circumstances. And it can be readily understood how
this has come about, if we consider the matter after the following man-
ner: It is well known that matter, by which is meant solid or semi-solid
substance of any kind whatever, if left to itself uninfluenced by any out-
side force, as gravity and the like, will assume the globular form. Thus
we find that the drop of water, of oil, or of metallic quicksilver, is round
or spherical, or nearly so. So we can understand that the silica deposited
as skeleton by the diatom would assume the spherical form. Likewise,
the minute markings or granulations made up by those siliceous particles
would, in a like manner, be at least spheroidal, be they elevations, as it is
assumed by some observers, or depressions, as is thought to be the case
by the majority of students. Now, supposing them to have a circular
outline when they are far apart, if they are made to approach each other
closer and closer until they touch, they, at last, by mutual pressure, will
present a six-sided outline. That such would be the case may be proved,
experimentally, in a very simple and, at the same time, elegant manner.
Let a mass of soap and water be placed in a bowl, and a pipe like a
straw be thrust down into it. Then if air be blown through the tube,
keeping the end opposite to that placed in the mouth in contact with the
bottom of the bowl, after a time the vessel will become filled with soap-
bubbles all of about one size, and which we know, if they had been
formed separately, would each have been perfectly spherical,—as, in fact,
can be seen on the top where those which are outermost present an outer
limiting surface which is part of a sphere. But we see plainly that these
little globes have pressed upon each other to such an extent that they
have lost their spherical outline, and have sides which are more or less
plane. If, now, a plate of glass be pressed down upon the accumulation
of bubbles in the bowl, many of them will be cut in two in such a way
that we may see through the glass that their section is an almost regular

428 PHYSICAL GEOGRAPHY.

hexagon. In fact, such a collection of bubbles, thus cut in halves, looks
very much like the transparent siliceous membrane of a diatom. It is
impossible, however, to give any idea in words of the beauty of the
diatomacez, and, in fact, the best of illustrations affords but a faint notion
of them; they must be seen and closely observed to be fully appreciated.
Their great interest to all students of nature will perhaps be understood
from a perusal of this brief sketch, wherein their principal points of
structure, habits, modes of occurrence, and uses, are set forth in such a
way, it is hoped, as will be readily understood, and at the same time
prove interesting to others than those intending to be students of these
organisms.

Having now arrived at a pretty clear idea of the typical structure of
diatoms in general, let us make ourselves more thoroughly acquainted
with some of the various forms in which they make their appearance.
If we take, as a representative of the usually free circular or discoid dia-
toms, the genus Azlacodiscus, we find the valves perfectly round in out-
line, and usually only slightly convex near the margin, the concavity for
holding the cell-contents being thus somewhat flattened, its sides being
limited as usual by the connecting membrane or zone, which in this
genus is narrow. The structure of the siliceous material which goes to
make up the valve is of the following character: On the exterior is a
plate marked with coarse hexagons, which really are only net-like; that
is to say, they merely constitute a hexagonal framework of boxes without
tops or bottoms, set side by side, and arranged more or less regularly, so
as to radiate from the centre to the edge of the valve. The radiant
arrangement of these coarse markings varies in regularity in the differ-
ent species of the genus, but in all is apparent. Inside of this coarsely
marked plate is another, so that the large hexagons have the character of
honey-comb; that is to say, the sides are perpendicular to the flat surface
of the inner plate, which thus constitutes for them a bottom. And this
inner plate is commonly, although not always, constructed after the same
manner as the outer one, being set all over with small hexagons, which
are so small that as yet their character has not been studied, but most
likely it is similar to the larger ones, that is to say, being honey-comb-
like; but its hexagons probably have not in their turn still smaller mark-
ings within them. At any rate, in most species of Azm/acodiscus, both

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NATURAL HISTORY OF THE DIATOMACE:, 429

those with two sets of hexagonal markings and those with only one set
of coarse ones, we find that under, and often filling up the whole bottom
of each hexagon, and therefore on the inside of the inner plate, is a little
plano-convex lens of silica. That such is the case is readily proved by
the images formed of the source of light, as a candle, by the little lenses ;
and in fact it would doubtless be possible to measure their focus by
means of a graduated fine adjustment to the microscope, such as is found
on the larger instruments. Sometimes the sides of the large hexagons
are not quite perpendicular to the inner plate, but approach each other as
they descend, so that the bottom of the cavity becomes concave; and, as
the convexity still occurs on the inner surface of the inner plate, we have
a meniscus lens of silica formed,—that is to say, a lens which is still
thickest at the centre, and therefore one which converges light like the
plano-convex one more commonly found. The effect on light passing
through such a diatom is very much the same as in the first case men-
tioned, but sufficiently different to be distinguished. Though these
peculiarities of structure can be made out by a careful observer in Aw/a-
codiscus and a few other genera, on account of their size and coarseness
of structure, yet they can be seen only with difficulty in others, and in
most diatoms cannot be shown at all. And this can be readily under-
stood when we remember that markings of any kind upon many species
can only indistinctly be seen when the best optical appliances for illumi-
nation and the finest microscope objectives and occulars are used. In
fact, it has been for the purpose of exhibiting such markings that objec-
tives have been specially made and apparatus invented, as has been
already said.

The sculpture of the siliceous cell-wall just described is not peculiar
to the Awlacodiscus, but is found in many other genera. This particular
genus, however, is remarkable for possessing what have been called, for
want of a better name, “feet.” These consist of tubular masses of silica
projecting outwards from the cell-wall, and usually placed near to the
margin of the valve. In some species the portion from which the feet
project is somewhat raised immediately under each foot, or in the form of
a ridge all around the valve. Within this portion the valve is either
plane, concave, or undulate, although the central portion is usually some-
what raised. The feet project outwards at a greater or less angle, and

430 PHYSICAL GEOGRAPHY.

are either short and stout or long and slender, varying in this respect in
different species. They also vary in number from one upwards, the
number being constant in some species, while in others it varies very
greatly. Usually the outermost end is somewhat swelled into something
like a knob, and within this part the central canal, running through the
foot, also swells into a spherical cavity. When a perfect specimen of an
Aulacodiscus is examined on what is known as its “front view,” that is to
say, with the edge of the valve presented towards the eye, the presence
of the feet makes the appearance of this diatom very characteristic. The
description of this genus has been thus full, because the beautiful com-
plexity of the diatomacez could thus be made evident, and many points
of structure dwelt upon at the outset. So when we come to describe a
few of the other forms as types, their resemblance to or variance from
Aulacodiscus will be noticed.

The genus Coscinodiscus has the same general characters of outline
and sculpture of markings as the genus just described, but is destitute of
“feet,” and, therefore, of the raised portion upon which they are placed.
The two membranes are present, but the inner one is smooth. Both
Autacodiscus and Coscinodiscus are inhabitants of salt water, although
there is a minute form, usually classed as a Coscinodiscus and called
minor, which has been seen in fresh water; but it is now pretty well
ascertained that it is not a true Coscinodiscus, but belongs to the genus
to be described next.

In Melostra, the frustules have a general resemblance to Coscinodiscus,
and are frequently mistaken for specimens of that genus, especially when
dead and detached one from the other. Usually, however, the valves are
so much more convex when viewed edgewise, that the whole frustule
may approach in form a sphere, as is the case in the species chosen as
an illustration. It however differs widely from Coscinodiscus in having
its frustules united, by means of their valves, into long chains, which are
quite flexible, so that they wave about in the moving water. Some
species have the valves more flat, and then the live plant looks like a
number of pill-boxes attached together. Some species are peculiar to
fresh water, whilst others are found in the sea; but it would seem that a
few of them can become acclimated to and live in either kind of water.

Actinoptychus, another beautiful genus, contains several species which

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NATURAL HISTORY OF THE DIATOMACEE. 431

are extremely graceful in sculpture. In form it is discoid, on what is
known as the “side view,” but, unlike any of those we have seen so far,
the surface of the valve is divided into segments which radiate from the
centre, and are arranged alternately elevated and depressed, so that on a
front view the frustule appears undulate. When we look straight down
upon the valve, it has very much the appearance of a wheel. In some
species the markings of the raised segments are different from those on
the sunk portions, while others have the markings of the same character
all over the valve. They are, however, always of the same general char-
acter as those described as occurring in Aw/acodiscus. This is likewise
a marine genus, and some of the most beautiful species belonging to it
have been found as yet only in the fossil state.

There are many other discoid forms which we cannot stop to describe,
but must pass on to consider some other genera.

Nearly allied to the true discoid diatoms, and in fact having a few cir-
cular species, are two genera which it will be well to describe here. One
of them is called Biddulphia, and is found only in salt water, although
one species was seen by the late Prof. Bailey in the Hudson river at
West Point, where the water is not all salt; but, strange to say, the tide
reaching up as far as this, the salt water creeps up under the fresh, so
that at this point salt and fresh water forms of vegetation appear along-
side of each other. Lzddulphia grows in chains attached to submerged
objects, more commonly the larger plants. It has valves either orbicular,
elliptic, or more or less pointed in two directions, and approaching in
outline to the boat-shaped genera to be presently described. In fact,
the outline of the valve in Biddulphia varies very greatly, as is seen by
the figures given. At two opposite points on the valve are projections
upwards very much like the feet of Awlacodiscus, and, in fact, they may
be considered their analogues. So when Biddulphia is looked at on a
front view, it looks like a number of little wool-sacks; and the species
which Prof. Bailey found at West Point, and which is not very uncommon
along the Atlantic coast of the United States, has very much that appear-
ance, especially as the frustules grow in the form of a chain, with these
projecting portions united, often alternately, so that the chain becomes
of a zigzag form. Sometimes the surface of the valve also bears upon
it certain spines, varying in number in different species, and usually

432 PHYSICAL GEOGRAPHY.

placed near to the centre or at points midway between the centre and
the edge, and half-way between the horn-like projections.

In outline, Bzddulphia passes into a genus known as 77yiceratium,
which, as its name indicates, is provided with three projecting horns or
corners. In fact, what may be called the normal form of its valve is
triangular, having three horn-like projecting portions like the two in
Biddulphia. But although the commonest outline is triangular, we find
certain species varying to such an extent as to have examples with four,
five, and even six sides,—in this respect resembling Az/acodiscus, whose
number of projections, or “feet,” vary in the manner described. And
there is a genus called Amphitetras, which apparently only differs from
Triceratium in the fact that its normal form is with four corners. In
truth, we find occasionally specimens of Biddulphia with three corners,
Triceratium with four, five, six, and even nine corners, and Amphitetras
with five corners, so it becomes extremely difficult to draw lines of dis-
tinction between these three genera. Besides this, we find that among
themselves the species of Zyceratium differ in minor characters; some
have the sides convex, becoming more and more so, until at last we havea
perfectly circular outline still retaining the three projecting horns. Then
we find them with sides straight, then more and more concave, until the
valve appears to be but three arms united by a very small body. Some
have undulate sides. The front view is as various as the side view. In
some the processes are nearly level with the surface of the valve, while
others have them considerably elevated, and attenuated into spines. So,
again, in this beautiful genus, the sculpturing of the valve is very various.
We have coarse hexagonal reticulations, with or without finer ones within
them, fine hexagonal markings, circular, dot-like, radiant or curved depres-
sions, in some cases of such delicacy that high-power glasses are required
for their elimination. Then, again, we have large, heavy bars of silica
projecting across the valve in different directions, merely cutting off the
corners, or dividing the central portion in various ways. In short, 7ricera-
tium is one of the most variable as it is one of the most beautiful genera
of the diatomacee. It is found living in the ocean, growing in chains
attached to alge and shells, after the manner of Biddulphia and Melosira.
Some of the most beautiful species have been as yet found only in the
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NATURAL HISTORY OF THE DIATOMACEE, 433

As has been said, the species of Aiddulphia vary very greatly among
themselves, until we have them approaching the boat-like form in outline,
and in this way they are connected with the next group of diatoms, which
we now come to consider. These are all more or less quadrangular in
outline, or, rather, we might describe them as elongate, with more or less
parallel sides, and having their ends acute or rounded. The genera
belonging to this group are very numerous, but we shall describe only a
few of them. It is a remarkable fact, that, almost with the exception of
some of the JZe/ostre and allied cylindrical forms, the discoid, two-, three-,
four-, five-, and six-cornered genera are confined to salt water; but the
boat- and stick-like forms are found in both fresh and salt water, so that
in our streams and ponds we find the “naviculeform” and “bacillar”
genera, as they are called, almost unmixed with circular forms. A few
species of J/closire, and an allied genus called Cyclotel/a, are found
occasionally intermixed with the boat-like ones, and rarely alone in lakes
and fresh-water streams. So we already see that, by examining the
species of diatoms, we can say with considerable certainty whether a
piece of water be fresh or salt, and, if found in a fossil condition, whether
the earth, of which they make up a part or the whole, was thrown down
from a now extinct ocean, lake, or river. Our knowledge of the habits of
the diatomacez is hardly complete enough as yet for us to tell exactly the
character of lake, river, or ocean in which the diatoms grow; but already
we have learned that certain forms are found on mountain tops, others in
swift streams, and so on.

Taking Pixnularia as the first type of the naviculeform, or boat-
shaped diatoms, we find it to be, of course, made up of two siliceous
valves and a connecting membrane. The valves are boat-shaped in
outline, sometimes with the sides parallel, and the ends pointed or
rounded off. Irequently the sides are convex or bowed outwards, bent
inwards, or undulate; but all of the various species, and they are very
numerous, preserve the general characteristic boat-like form. The valves
in this genus are commonly very convex, so that when looked at on a
front view or endwise, the edges are distinctly rounded off. Running
down the middle portion of the valve from one end to the other is a
blank space, which, at each end and at the centre, expands into round

nodules projecting into the cavity of the frustule, as likewise does the
VOR Te 4.87

434 PHYSICAL GEOGRAPHY.

blank strip itself. In fact, this strip, with its end and middle swellings,
constitutes a thickened part of the valve, and they have by some writers
been called the “median line,” and “central” and “terminal nodules.”
Considerable confusion has arisen in the nomenclature of what might be
called the osteology of the diatomacea. This central thickened band is
usually, if not always at some period in the life of the individual, traversed
by a canal which runs the whole length of the clear space, but in the
thicker ends terminates in enlargements, and is divided into two sections
at the centre of the valve, where, likewise, it ends in two round cavities.
The end enlargements of this canal have also been called “terminal
nodules,” and the swellings near the centre have been called “central
nodules,” as well as the parts just described. Lately it has been proposed
to call the tube the “central canal,” and by this name we shall designate
it in this sketch. At one period in the life of the diatom it would seem
that this canal is open outwards down its whole length; at least, such is
the belief of some observers ; but the writer has never been able to satisfy
himself that such is the case, for in some of the Pinnularie he has
noticed that the central enlargements of this canal open, by means of
trumpet-shaped tubes set at right angles to the course of the canal, into
the general cavity of the frustule, and that the terminal expansions, in a
like manner, have a communication outwards at the ends of the valve.
It is his opinion that this canal has something to do with the motion of
the naviculeeform diatoms, which always sail about in a direction parallel
to their longest axis. The central canal, when the diatom valve is dead
and dry, is filled with air, and then,—on account of the effect produced
upon the light as it is transmitted through the object to the microscope—
appears black, or near ly so, if the objective employed is a good one, and
more or less colored when an inferior one is used. The markings found
sculpturing the valve of Pzuularia are different from what we have seen
to occur in any of the genera described so far. We find no large hexa-
gons nor finer ones here, but, instead, the valve is marked on each side of
the median blank space with lines which indicate elevations in the form of
bars or corrugations more or less parallel to each other, and set at nearly
right angles to the central canal. These bars, or “pinnulz,” as they are

called, reach from the edge of the valve over the convex margin, and up
to the median blank space, where they stop in rounded off extremities.

NATURAL HISTORY OF THE DIATOMACE#, 435

- There is a genus very closely allied to Pzxnularia which has the same
general form, except that in many of the species the sides slope off
straight towards the somewhat acute ends, so that the whole valve is
quadrangular in form. On account of the thickened portion at the centre
of the valve being widened out so as to extend almost or quite across the
valve as a band, and thus, with the median blank space, form a cross, it has
received the name of Stauwroneis. The markings on the valve, however,
are not those found on /Pzznzlaria, but consist of minute depressions,
or dots set in lines, which run usually somewhat sloping from the middle
portion to the edge. These rows of dots are usually known as “striz,”
and are often extremely fine, so much so that in some species in which
they occur they are very difficult to demonstrate, and hence the diatom
becomes a very good “test-object.” In MVavicula, the genus which has
by far the largest number of species, inhabiting fresh, salt, and brackish
water, we have S/auronezs without the central cross bar, but merely the
blank longitudinal space found in Péxnularia.

The variation in outline and in other respects, among the several hun-
dred species which have been grouped together under the generic name
of Mavicula, is very great, so much so, in fact, that it would seem reason-
able to believe that several genera must have been unconsciously fused
together. And such is the opinion of the present writer, in which he
rather agrees with some of the older writers on the diatomacez.

There is a genus which at one tim was included in Navicula, but
which has of late years been separated therefrom, and is known as P/en-
rosigma. It looks like a Wavicula which has been twisted so as to bend
the two opposite sides of the valve in different directions. Hence it has
somewhat the form of an S, as its name indicates. It has a central canal
like the other naviculeform diatoms; but the blank space through which
it runs is very narrow. The central expansion is generally present; but
the terminal swellings are not so evident. On this account, although in
Pinnularia and other genera, in which they are pronounced, the terminal
expansions of the blank, thickened portion have been called “terminal

>

nodules ;” in Pleurosigma, where they are not so apparent, that name
has been applied to the swelled ends of the central canal,—an example of
the unscientific manner in which the diatomacez have been treated by

many who have written about them.

436 PHYSICAL GEOGRAPHY.

The markings on the valves of P/ewvosigma are peculiar, and different
from those found upon the other naviculaeform diatoms considered. The
genus can be and is usually divided into two groups, distinguished by the
character of the markings. In the first group the valve is covered with
dots set all over the surface in such a way that they are in lines at equal
distances apart, running from the central canal to the edge of the valve.
But the next row starts, as it were, half a dot behind the previous one:
therefore its dots alternate with and come between those of the first line,
and so on, so that the dots are at equal distances apart all over the valve,
but, when traced across the valve, are in straight lines, and, when traced
lengthwise of the valve, are in zigzag lines. As these dots are coarse
and set far apart in a few species, they can then be seen to be circular,
but, when they approach each other closely, they appear to become, by
mutual compression, as would be the case if such were to occur, hexa-
gons. In fact, it has been one of the difficult matters to solve concerning
the diatoms, and one on which observers have differed for a long time, as
to whether the markings on certain species of Pleurosigma are circular
or hexagonal. Hence one species, especially named Pleurosigma angu-
lata, has been selected as a “test object” for lenses of moderate power.
But the second of the two groups into which Plewrosigma is divided has
its markings arranged somewhat differently. In this group the dots are
set in straight lines, if they be traced either across or lengthwise of the
valve; that is to say, instead of being alternate, they are opposite in con-
tiguous rows. Among themselves the different species of Pleurosigma
vary somewhat: thus in many the sides run in one unbroken line from
end to end, being only swelled out at the centre. In P. angulata, and
still more so in P. guadrata, the bowing out at this point is decidedly
angular. In P. Balticum, a species originally found in the Baltic sea, and
hence the name which was given to it, but which has since been found
pretty much all over the world, the sides are straight and parallel until
near the ends, when they are curved over so that one end of the valve
points to the right, while the other is turned to the left. P. angulata and
P. quadrata belong to the group in which the dots of the markings are
arranged alternately, while P. Balticum has its dots set regularly and
opposite to each other. P. fasciola differs totally in outline from any of
those described. The main portion of its valve is in shape like a Navic-

NATURAL HISTORY OF THE DIATOMACEE, 437

ula, being almost oval, but pointed at each end, and with a central canal
running down the middle, just like a Navicula; in fact, it may be said to
be almost shuttle-shaped; but from each extremity projects a long, horn-
like portion, into which the central canal is continued, and which is
curved one to the right, the other to the left, thus completing the sigmoid
form necessary to constitute a member of this genus. Some species of
Pleurosigma have markings of such extreme fineness that it becomes
very difficult to see them unless the microscope employed be of the best
quality. A few species are found in fresh water, but for the most part
they are inhabitants of the brackish water of swamps and similar localities.

Some species of diatoms present us with examples of a peculiar struc-
ture not found in all. Thus, when we look at certain species of Stauro-
nets from a front view, we see at the ends and just below the terminal
nodules, as a part of the valve, and just where it joins the connecting
membrane or zone, a stout siliceous structure projecting a short distance
into the cavity of the frustule like a shelf, but more so at the ends than
at the sides, where it becomes so shallow as to be hardly apparent.
When we look down upon the valve, or view the diatom on what is known
as the side, we see that this projecting portion forms a ring all around
the cavity, widest at the ends and narrowest at the centre, where it is
hardly, or in some species not at all, perceptible. This has been called
the “septum.” In 77iceratium, we find it appearing only as slight project-
ing shelves at the corners. Some genera have it very strongly developed,
and projecting very far into the cavity, so that the two septa divide it
into three distinct portions. Some genera have more than two septa,
and in such cases they are not fused with and form part of the valves,
but are attached to separate rings which lie between the edges of the
valves and the connecting membrane or zone.

Septa are very marked characters in a genus named Grammatophora,
which is found in chains of many frustules, united corner to corner, and
attached to algae in the ocean on almost all sea shores. The valves are
shaped somewhat like a Pinnularia, but have the strize, as the rows of
markings have been called, running straight across, and extending quite
up to the ends. The septa are four in number, and extend almost across
the cavity of the frustule, leaving only a small opening of communica-
tion at the centre. Besides, although some species have them straight,

438 PHYSICAL GEOGRAPHY.

in most they are undulate, so that on a front view they look somewhat
like written characters, which has led to the name Grammatophora being
given to the genus.

Nearly related to the genus just mentioned is one known as Khabdo-
nema. It likewise is found growing in chains attached to alga, and
similar submerged objects in the ocean. In this the septa are not con-
tinuous, but look as if they were punctured with several holes. The two
last mentioned genera are attached to their supports by a small gelati-
nous cushion, but there is a genus named Achnanthes, in which this
cushion is lengthened out into a long stalk, and as it is attached to one
of the corners of the frustule, the whole individual looks very much like
a flag floating out straight from a staff. This stalk is called the “stipes,”
and is remarkably developed in other genera. Thus, Gomphonema con-
sists of a number of wedge-shaped frustules attached by their pointed
ends to long and forked stalks, while in Syxedra the stipes has again
shrunk down to a cushion. The frustules of Syaedra are like little sticks
attached to the cushion by one end, and sticking out on all sides like the
spines of a porcupine.

There are many other forms which the various genera of diatoms
present, but we have had space only to describe and figure a few of them.
The possessor of a microscope will soon, if he searches, come across
others; and if he is encouraged to ask for more information concerning
the beautiful atomies he sees, as it is to be hoped will be the case, he will
be able, in the works of W. Smith, Rabenhorst, Kiitzing, Ralfs, and others,
to find them more fully described, and better and more thoroughly illus-
trated. So to those works we must refer the reader who desires to learn
more than we have been able to tell him in this little sketch concerning
the diatomaceze.

Pak 2 oC OND:
MovEMENTS OF THE DIATOMACE.

It has been said that it is extremely probable that all species of dia-
tomacez are at some period of their lives free, while for a short period
perhaps for some, but always for some time, they are fixed or attached to
some submerged object, as rocks, plants, woodwork, or similar substances.
This opinion is not held by all observers ; so much so that many,—and

NATURAL HISTORY OF THE DIATOMACE., 439

W. Smith, the author of the Synopsis of the British Diatomacez, among
that number,—have classified them in such a way as to constitute two
great groups, namely, those which are free, and those which occur
attached. It would seem most natural that those forms which commonly
present themselves attached should become free at some period of their
existence for the purpose of disseminating the species, for we do not find
that the diatomacez produce seed which may be wafted about by the
motion of the water, or young which are specially characterized by pos-
sessing organs of motion, so that this phenomenon may be accomplished.
However this may be, it is a fact that many of them possess peculiar
movements, produced by and inherent in themselves, and which have
from the earliest times, when they were first observed, attracted the
attention and aroused the wonder of possessors of microscopes. And
when these seeming sentient movements are watched by means of the
magnifying glass, it is not to be wondered at that many observers have
been disposed to class them among animals possessing complicated organs
of locomotion, digestion, and reproduction, if not reasoning powers to
guide and direct those organs. And this power of active movement is
not confined to those forms alone which are usually seen free, for many
of the fixed forms, if detached from their support, will immediately take
upon themselves motions precisely similar to those of their normally
free brethren.

The extreme liveliness of some of the diatomacez has been considered
by many as proof of their animal nature; but when we know that the
seeds of many large and acknowledged plants growing in water, namely,
the alge, are even more active in their motions than our little friends, and,
as in the case of those plants, this motion is evidently for disseminating
the species, so we may naturally believe that some similar provision is
made for the wide spreading of the diatomaceze. If we watch, by means
of a good microscope, an individual belonging to the genus Vavicu/a, in
which the form, when viewed in the direction which is usually presented
to the eye, is that of a double-prowed boat, something like an Indian
canoe, we find that it moves after the manner of a boat, but with either
prow forward, as happens to be most convenient, apparently, for, after
moving in one direction for a few seconds or minutes, it will immediately

return upon its course, now propelling the other forward. And although

440 PHYSICAL GEOGRAPHY.

in a few species, and those seemingly the larger, the motion is a steady
progressive one, yet it is by far commoner to find that it is unsteady and
trembling, as if it were the tottering steps of the infant, or of extreme
old age. Navicula is one of those genera which are usually classed
among the free forms, and in them all, with perhaps one or two excep-
tions, when they have any progressive motion, it is that which we have
described. There is a genus which has very much the form of a horse
saddle with the two flexures, and known as Campylodiscus, in which “the
motion never proceeds farther than a languid roll from one side to the
other.”

As has been remarked, the earlier observers of these atomies, being
insufficiently informed on the subject of the economy of the vegetable
kingdom, considered the possession of the power of spontaneous motion
by any being indisputable evidence of its animal nature; and, on this
foundation, it became easy to rear up a mass of proofs that the diatoma-
cez were certainly animals. The space within the two-valved shell, like
an oyster or clam, was the animal matter furnished with special organs,
if not with muscles, by means of which the movements were accom-
plished. Of course, the many clear vacuole-like-looking spots of oily
matter were the stomachs, and, with the imperfect microscopes of the
time, observers were (they thought) able to see the protrusion of a “foot”
like that upon which the snail travels, through the central portion, which
looked to them like a round opening, but which we now know to be a
thickened portion of the shell. A late observer has asserted that he has
seen, along the so-called “median line,” an appearance indicating the pro-
trusion of an organ or series of organs of some kind; but as others,
equally competent microscopists, have not been able to satisfy themselves
that there are such organs, this gentleman's assertion can hardly be said
to be proven. There are still a few microscopists who hold to the belief
in the animal nature of the diatomacez, although by far the majority
rank them as plants. One gentleman in England says that he has
seen (and, what is more, figures) the cilia, or hairs, which move about
like arms, and by means of which these creatures change their place.
Unfortunately, he first takes the animal nature of the diatomacez for
granted, and then attempts to prove the existence of the cilia as organs
of locomotion.

NATURAL HISTORY OF THE DIATOMACEE. 44!

It will be naturally supposed, from what has been said on the subject,
that the mode in which the motion is caused is not decidedly known;
but however that may be, it is a remarkable characteristic of these crea-
tures, and, although in most species it is regular and uniform, in some it
takes place as a series of jerks. It would seem that it could hardly be
called a voluntary motion, or, at least, that if it be so, the faculty govern-
ing and directing it within the creature is of a low order, or one which
responds to stimulus in a very sluggish manner ; for if an obstacle of any
kind occur in the path of a moving diatom, like a Mavzcu/a, it is not
avoided; but, on the contrary, if it be small enough, it is thrust aside;
or, if it be too large, the diatom is arrested in its career for a certain
length of time, or turned aside in its course. If it be stopped, it isa
remarkable fact, noted by English observers, that the diatom waits exactly
the length of time it would have taken for it to perfect its forward pro-
gression to the greatest extent, when it returns on its path again. In
many species, however, the motion is not so regular as this, and the little
creature goes tottering along its way. It has been remarked by one
author that “the movements of the diatomaceze appear rapid and viva-
cious under the microscope; but it must be remembered that the high
powers usually employed in the observation of these minute organisms
magnify their motions as well as their bulk.” Using a seconds watch,
and timing several species exactly, it has been found that one of the
most rapid, known as Bacillaria paradoxa, took a whole second to move
over one two-hundreth of an inch; and that one of the slowest, named
Pinnularia radtosa, in the same space of time only travelled one thirty-
four-hundredth of an inch ;—so that the quickest would take three min-
utes to travel an inch, while its slowest relative would require a full hour
to perform the same feat. But although a few observations of this kind
have been made, we have by no means arrived at a knowledge of the
rate of movement of these atomies, for it varies under different circum-
stances, as apparent condition of health and surroundings. Heat appears
to accelerate as cold retards it; and yet I have seen Bacillaria paradoxa
very lively when taken from beneath the ice on a cold winter’s day. It
is a curious fact, that often, as we watch a diatom sailing across the field
of the microscope, it comes in contact with an obstacle, as a grain of

sand, If it cannot move it, or pass under it, or, by a little shifting, around
VOR; 5G

442 PHYSICAL GEOGRAPHY.

it, it waits exactly the length of time it would have taken for it to perfect
its forward progression, when it returns on its path again. But this takes
place only with such species as have a regular backward and forward mo-
tion; most of them are extremely erratic in their ways. As an illustration
of the regularity of movement of the diatomacee, let us consider one of
those species just mentioned, namely, Bacillaria paradoxa. ‘This crea-
ture has a motion of its own, which is so peculiar, and at the same time
so incomprehensible in its mode of accomplishment, that it well deserves
a more particular description. This species is somewhat of the form of
a straight ruler, when we consider the single individual, or, at least, it
looks very much of that form, as commonly seen. But a careful exami-
nation shows it to be made up of two long and narrow boat-shaped valves,
united together so that the keels project outwards opposite to each other,
and enclose within their united bodies the general cavity of the frustule.
When in a living state, the compound individual, or colony, whichever
we may choose to consider it, consists of a number, more or less great,
of these double boat-shaped frustules, united one to the other at their
keeled sides; but the mode of union is entirely unknown, and, from the
extreme freedom of motion which each frustule of the colony enjoys, it
is hard to imagine what its character is. Thus united, they form a fila-
ment which is generally found floating freely in the water of brackish
ditches within reach of the influence of the sea. But I have seen it in
perfectly fresh water, far up the Hudson river in New York state.

The movement has been well described by an English observer, Mr.
Thwaites, and I cannot do better than quote his words. He says,—

When the filaments have been detached from the plants to which they adhere, a
remarkable motion is seen to commence in them. The first indication of this consists
in a slight movement of a terminal frustule, which begins to slide lengthwise over its
contiguous frustule ; the second acts simultaneously in a similar manner with regard to
the third, and so on, throughout the whole filament; the same action having been going
on at the same time at both ends of the filament, but in opposite directions. The cen-
tral frustule thus appears to remain stationary, or nearly so, while each of the others
has moved with a rapidity increasing with its distance from the centre, its own rate of
movement having been increased by the addition of that of the independent move-
ment of each frustule between it and the central one. This lateral elongation of the
filament continues until the point of contact between the contiguous frustules is
reduced to a very small portion of their length, when the filament is again contracted

NATURAL HISTORY OF THE DIATOMACEZ. 443

by the frustules sliding back again, as it were, over each other; and this changed
direction of movement proceeding, the filament is again drawn out until the frustules
are again only slightly in contact. The direction of the movement is again reversed,
and continues to operate in opposite directions, the time occupied in passing from the
elongation in one direction to the opposite being generally about forty-five seconds.
If a filament while in motion be forcibly divided, the uninjured frustules of each por-
tion continue to move as before, proving that the filament is a compound structure,
notwithstanding that its frustules move in unison. When the filament is elongated to
its utmost extent, it is extremely rigid, and requires some comparatively considerable
force to bend it, the whole filament moving out of the way of any obstacle rather than

bending or separating at the joints.

This is not always the case, as I have myself frequently observed, as
the filament often becomes bent by the force of its own motion. And
there is one other fact which seems to have escaped the notice of Mr.
Thwaites, and which adds considerably to the interest of an exhibition
of this plant while in motion. After the extended frustules have returned
to their normal position in the filament, so as to form a ribbon-like com-
bination again, and just at the time when they are about to start on their
way in the opposite direction, there seems as if a considerable amount of
force were necessary to get them started past this point, for this force is
very apt to dislodge the whole filament and swing it entirely round, so
that that end which was, we may say, pointing towards the right hand,
now points to the left. The consequence is, that now, when the frustules
proceed on their path towards the opposite side of the filament from
which they projected previously, they, in reality, extend towards the same
side of the microscope as they returned from. This motion often contin-
ues to be exerted, so that the whole filament is periodically swung around
on its centre as the frustules return to their places, and become again
parallel one to the other. Often and often have I spent hours looking at
this marvel of nature; the motion without apparent cause or mode, an
invisible joint, which, as a friend of mine (an engineer) once remarked,
would be a fortune to any one who would discover it, for here we have
several sticks forming the bundle, moving over each other without sep-
arating, and yet the use of the highest powers of the microscope has
failed to detect the means of their union into one mass, or composite
group, of individuals. The more often I watch Bacilleria paradoxa, the
more it puzzles me. Not long since I saw one specimen (of course, I

444 PHYSICAL GEOGRAPHY.

mean one bundle of individuals) slide out to its utmost limit across the
field of view, and then, becoming entangled with others, which likewise
were made up of many individuals, some eight or ten of its frustules
were twisted around, almost off from the rest, so as to lie at right angles
to them; and when the group containing the largest number of frustules
receded to their former position, which they soon did, the eight or ten
seeming, by the act of twisting, to lose their power of motion among
themselves for the time being, were dragged along in a helpless condi-
tion, and twisted completely around one revolution, so as thereafter to
fall back again into their places, when all went on again as usual,—that
is to say, the regular motion of all the frustules over each other succeeded.
Now what kind of a joint can it be that permits of such eccentric move-
ment? The motion of all diatoms is accelerated by a moderate heat, so
that specimens gathered during the winter months, and remaining either
quiescent, or only exhibiting very slight motion when viewed by means
of the magnifying glass of the microscope, may be made to move vigor-
ously by the cautious application of warmth, as by placing them in a
warm room, or by holding the glass slide, upon which they are, upon the
palm of the hand for a short time.

a Oa lat so SB:
Mover oF GROWTH OF THE DIATOMACE.

When we speak of the growth of the Diatomacezx, it must not be
confounded with the reproduction of the organisms, although modern
physiologists are coming to understand that growth or increase in vol-
ume, and reproduction or increase in number, are very nearly related, if
they be not but modification, in degree and in direction, of a force acting
within and essential to the existence of living beings.

We have seen what the structure of the outer coat or siliceous skeleton
of the diatomaceze is. Let us now, before asking how they grow or
increase in dimensions, learn what is known with regard to their internal
economy, that is to say, the anatomy of their softer parts. Unfortu-
nately, on this point our knowledge is extremely unsatisfactory, and it
even appears, as has been already hinted, that the result of modern
investigations would be to upset a great deal of what we have up to a
late date considered as settled in connection with this point.

NATURAL HISTORY OF THE DIATOMACE, 445

Immediately within the siliceous skeleton of a diatom is supposed by
many to be a membrane or skin which bounds and limits the soft parts of
the organism; and it is this membrane, say those who believe in its exist-
ence, which secretes or forms the wonderfully sculptured epiderm we
have been considering. Some observers think that there is also an out-
side membrane, and that it is in it that the silica accumulates. But as
many good observers have been able to see neither of these membranes
in the living diatom, and as even the believers in their existence acknowl-
edge that they are extremely difficult of exhibition, most likely the fact is
that the real individual matter of the diatom is a mass of structureless
protoplasm, which deposits near its outer portion the silica it has absorbed
from the surrounding water. Within the protoplasmic mass is the endo-
chrome or colored matter we have already spoken of, and which is most
commonly disposed in two portions contiguous to the two valves. In the
clear central portion there is often to be seen a little sac or vesicle, which
is quite transparent, except at one part, where a minute dot is seen. This
vesicle is considered to be the “nucleus” of the diatom, while the dot is
the “nucleolus,” both of these things being required in a cell constituted
under the type established by a German observer named Schwann. But
now that Schwann’s typical cell, consisting of a “cell wall” containing
“cell contents,’ wherein are found a “nucleus” and often one “nucleolus”
or several “nucleoli,” is known to exist rarely, we are not surprised if
we do not find all of these parts present in a diatom. And now that
we understand the internal anotomy of the diatom, without taking into
consideration disputed minutiz of structure, we can see how the indi-
vidual grows.

Schwann has shown us what he considers cell growth to be, and it
is what is known as “cell subdivision.” That is to say, the cell itself is
stable as to size, but increase of volume occurs by its dividing into two,
and these two into four, and so on, so that if the resulting cells remain
united to each other there will eventuate a true increase in bulk, and
eventually a large organism like a tree or a man may be formed. But
such is not the way that the diatom grows, for it is not a polycellular, but
a unicellular organism. There is a large group of very simple plants,
even more simple in structure than the diatomacez, for they have no
elaborately sculptured siliceous cell-wall, which are known as Protophytes,

446 PHYSICAL GEOGRAPHY.

and in the life history of one of these we shall be able to study the sim-
plest expression of cell growth. Dr. Carpenter, whose valuable treatise
on the microscope is to be recommended to all intending to use that
instrument, has epitomized what is known on this subject so well that I
cannot do better than to give it in his own words. He says,—

The life-history of one of these unicellular plants, in its most simple form, can
scarcely be better exemplified than in the Palmoglea macrococca (Kiitzing)—one of
those humble kinds of vegetation which spreads itself as a green slime over damp
stones, walls, &c. When this slime is examined with the microscope, it is found to
consist of a multitude of green cells (Fig. A), each surrounded by a gelatinous envel-
ope; the cell, which does not seem to have any distinct membranous wall, is filled
with granular particles of a green color; and a wwuclews, or more solid aggregation,
which appears to be the centre of the vital activity of the cell, may sometimes be
distinguished through the midst of these. When treated with tincture of iodine,
however, the green contents of the cell are turned to a brownish hue, and a dark
brown nucleus is distinctly shown. Other cells are seen (B), which are considerably
elongated, some of them beginning to present a sort of hour-glass contraction across
the middle; in these is commencing that curious multiplication by binary subdivison,
which is the ordinary mode of increase throughout the vegetable kingdom; and when
acell in this condition is treated with tincture of iodine, the nucleus is seen to be
undergoing the like elongation and constriction. A more advanced state of the pro-
cess of subdivision is seen at C, in which the constriction has proceeded to the extent
of completely cutting off the two halves of the cell, as well as of the nucleus (1), from
each other, though they still remain in mutual contact; but in a yet later stage they
are found detached from each other (D), though still included within the same gelati-
nous envelope. Each new cell then begins to secrete its own gelatinous envelope, so
that, by its intervention, the two are usually soon separated from one another (FE).
Sometimes, however, this is not the case,—the process of subdivision being quickly
repeated before there is time for the production of the gelatinous envelope, so that a
series of cells (F) hanging on one to another is produced.

Now the diatomacez grow in a manner precisely similar to that just
described as taking place in Pa/moglea. This subdivision of the cell, so
that the new individuals are formed from one in the diatomacez, results
in the production of a series of frustules almost identical in all particulars
with the original individual. In most cases, if not in all, the new indi-
viduals differ from that from which they sprung in two marked respects:
First, they each possess one old and one new valve; and, secondly, the
new valve is smaller than the old one, so that the two valves of all dia-
toms differ somewhat in dimensions, although alike in other respects.

NATURAL HISTORY OF THE DIATOMACEE, 447

As the siliceous exterior skeleton of the diatom does not permit of its
expanding in all directions, the consequence is that when it absorbs nutri-
tive material, increases in bulk, and proceeds to subdivide, it must mul-
tiply its bulk in one direction only; and, as the two valves are capable of
being separated one from the other along the line of junction with the
connecting membrane, it is in that way that the splitting up of the cell
into two new ones takes place. The existence of the connecting mem-
brane in the perfect diatomaceous individual, before subdivision starts, is
denied by many. Under those circumstances, the siliceous skeleton con-
sists of only two parts, the valves, to which, as soon as subdivision sets
in the third portion, the connecting membrane is added. In Palmoglea
we have seen that the perfect cell subdivides by a process which shows
itself by the bending in of the cell wall, if there be one, or by the pe-
riphery of the mass, if there be no limiting membrane. In this way, at
first, two united and similar halves, and thereafter, two separate individ-
uals, are formed exactly alike in all particulars. The nucleus and nucle-
olus, if there be one, of the diatom subdivide at the same time; and, to
make room for the increasing cell-substance, the enclosing valves sepa-
rate from one another, the space all around between them being closed in
by the new hoop of siliceous substance, the connecting membrane which
now makes its appearance and grows by additions to its two edges, as the
accumulation of pabulum by the growing individual goes on. At the
same time, two new valves have been forming exactly like the two old
ones, except that in consequence of their forming entirely within the con-
necting membrane, which has the same diameter as the old valves, they
are just so much smaller; and, as this mode of subdivision is repeated
again and again, there are always two individual diatoms having one old
and one new valve, which latest formed valve is continually being replaced
by another still newer. That the cell-contents may be at no time exposed
to direct contact with the surrounding water, the connecting membrane
is formed of two pieces, by additions next to the two valves; and, as one
valve of the diatom individual is always somewhat smaller than the other,
one of these sections of the connecting membrane is smaller than and
slides within the other. In some cases, however, it would seem that the
connecting membrane is made up of but one piece, instead of two, as
described. On account of this gradual diminution in size which must

448 PHYSICAL GEOGRAPHY.

take place, we can readily understand how we shall be very likely to find
diatoms growing together which are exactly alike, except that they vary
in size. But instead of the smallest being the oldest, the largest were
formed first, and, by the process of subdivision described, they have grad-
ually diminished in dimension. And it would seem that there was a limit
in each species beyond which the frustule did not diminish, but as soon
as it was reached, then the stage had arrived when reproduction sets in
in the manner to be presently described. Thus we see how one indi-
vidual diatom may in a very short time populate a large lake or river;
but all of these separate cells, which have now become separate individ-
uals as well, will very closely resemble the first one from which they
sprung. But circumstances may occur, while this rapid growth is going
on, which may modify the characters of the diatom to such an extent that
very marked variation may result. Thus, for example, if the original
frustule existed at the head waters of a small stream, in perfectly fresh,
running water, some of its descendants may be carried down into a lake
where they may lodge along the shore, in still water, and thus become
modified, or, they may pass on into a large river, to be there affected, or
even carried down to its mouth, and there, where the salt and fresh waters
mingle, be changed by that circumstance. So, of course, other circum-
stances, which will readily present themselves to the mind, will serve to
form and perpetuate variation in the diatoms, until two frustules, de-
scended from the same progenitor, by growing under different circum-
stances, will appear so unlike that they may be classed as separate
species, or even as belonging to separate genera.

The time occupied in a single act of self-division in the diatoms has
not been ascertained for all species, although it has been lately noted for
a few; “but supposing it to be completed in twenty-four hours, we should
have, as the progeny of a single frustule, the amazing number of one
thousand millions in a single month,—a circumstance which will, in some
degree, explain the sudden, or, at least, rapid appearance of vast numbers
of these organisms in localities where they were but a short time pre-
viously either unrecognized, or only sparingly diffused.”

In all cases, however, the two newly formed frustules do not entirely
separate from each other, for, after subdivision has taken place, they
remain united, so that in time others will be added, and eventually a long

NATURAL HISTORY OF THE DIATOMACE., 449

ribbon-like assemblage of individuals result. The genera /ragz/aria,
Himantidium, and Rhabdonema, are examples of such a mode of growth
when the valves are oblong, and J7/e/ostva when they are circular. Then,
again, the separation may be partial, so that the frustules remaining
united by the alternate corners are attached to each other, and a zigzag
chain is formed. Déatoma and Grammatophora are examples of this.
If the frustules are not possessed of quite parallel sides, but if they, on
the contrary, approach each other at one end, and then remain united
after subdivision has taken place, a fan-shaped arrangement will result, as
is seen in Lichmaphora; or, if subdivision continues, a spiral will be
formed as in Meridion. Those forms which do not float about freely in
the water in which they live and grow, are attached to submerged objects
by either a small gelatinous cushion, a long single or branching stalk,
pedicle, or “stipes,” as it is called. And there are forms, as Schizonema,
which are of a naviculoid form, but which secrete around themselves a
membranous tube within which the process of subdivision goes on, and
up and down the cavity of which the little boats sail with extreme
activity. Thus, from this simple process of subdivision, as described,
various forms may result, and many individuals be formed which shall
have their number still further increased by the process of reproduction
to be next described.

PART Foun. es
REPRODUCTION OF THE DIATOMACEZ.

We have seen the manner in which the diatomacez increase in dimen-
sions, or grow, and observed that it is essentially the same process as
that which takes place in larger and apparently more complex organisms,
both animal and vegetable. That is to say, we have found that in the
case of the diatomacez it becomes very difficult, if not impossible, to
distinguish the results of growth from the results of reproduction. And
although at first sight this may appear a very remarkable fact, yet it
ceases to be so if we remember that really physiology teaches us that
reproduction is merely a form of modified growth, resulting after the
casting off from the parent’s body of one or more masses of matter which
possess in themselves the power of assimilation of food, and its appro-

priation for the building up and elaboration of new tissues. Those genera
VoL. i $9

450 PHYSICAL GEOGRAPHY.

of diatomaceze which occur normally, or, we should say, most com-
monly, attached in some manner, as by a cushion, pedicle, stipes, or the
surface of the valve or connecting membrane, or otherwise, to submerged
objects, would never become very widely distributed through the agency
of self-fission alone, as it has been described, and the consequence would
be that they would be confined to certain localities were there not some
other mode of increase or reproduction. To a certain extent, this distri-
bution is provided for by the curious movements of the individual which
we have just treated of, and which we have seen are quite lively in some
species. But it is still more perfectly insured by the process of repro-
duction in which a new individual is developed from a parent. It is in
the form of spores or seeds that most plants (or, at least, the larger ones
with which we are acquainted) are enabled to endure the severe frosts of
the winter months; and the same is likely to be the case with the dia-
tomacez, although it is true that some species are to be found living and
swimming actively about beneath the frozen surface of ponds and streams.
And, although they be caught within the mass of solid ice, yet their
vitality does not seem to be materially compromised, for, on thawing the
ice they again move about in a lively manner in the water formed. Very
little investigation has been carried on in the direction of the reproduc-
tion of the diatomacez, or, rather, we should say, that little has been
published in this connection, so that we have few authorities to draw
upon to enlighten us on this point in the economy of our little friends.
From what little has been observed and recorded by a few investigators,
it would seem that the diatomaceze reproduce after a manner very similar
to that which has been found to take place in the Profophyta, or simple
unicellular plants ; and this fact has been brought forward as an argu-
ment in favor of the vegetable nature of the organisms of which we
are treating.

The first instance in which the process of reproduction was observed
and published was by Mr. Thwaites, in Zpzthemta, a genus which is
almost always found in the living state, attached to submerged plants, as
mosses and the like. He found it to be essentially the same as the mode
of conjugation, as it had been called, known to take place in several alge
or water plants of simple organization. He describes it in the following

manner: “The process of conjugation consists in the union of the endo-

NATURAL HISTORY OF THE DIATOMACEE, 451

chrome of two approximated fronds [using this term instead of frustule,
to indicate the perfect individual], this mixed endochrome developing
around itself a proper membrane, and thus becoming converted into the
sporangium.” The sporangium is what may be called the seed vessel, as,
although it does not contain seeds, in the ordinary acceptation of that
term, yet from it proceed the new individuals who are to perpetuate the
species. “Ina very early stage of the process, the conjugated frustules
have their concave surfaces [it must be remembered that we are speaking
of Epithemia, whose outline is somewhat bow-shaped, having convex and
concave surfaces] in nearly close opposition; and, it may be observed,
that from each of these surfaces two protuberances arise, which meet two
similar ones in the opposite frustule; these protuberances indicate the
future channels of communication by which the endochrome of the two
frustules becomes united, as well as the spot where is subsequently devel-
oped the double sporangium, or, rather, the two sporangia. The mixed
endochrome occurs at first as two irregular masses between the connected
(conjugating) frustules; but these masses shortly become covered with a
smooth cylindrical membrane, the young sporangia, which gradually in-
crease in length, retaining nearly a cylindrical form until they far exceed
in dimensions the parent frustules, and, at length, when mature, become,
like them, transversely striated upon the surface. Around the whole
structure a considerable quantity of mucus has during this time been
developed, by which the empty frustules are held attached to the sporan-
gia.” Thus we see that, whether any two particular frustules are drawn
towards each other or not (which we do not know), yet two contiguous
individuals pour out their respective contents, which, melting together,
are thus fused into a mass, around which is formed one or two new sili-
ceous coats exactly alike in structure, but only differing in size, being
larger than those which enclose the parent frustules. Enveloping these
sporangia, or large cases from which the new individuals shall be evolved,
is thrown a protecting, or, perhaps, nutritive globular mass of transparent
mucous material. In different genera, slight variations are met with in
the method of conjugation, as described. Thus, in some species of Gom-
phonema, which grows attached to the end of branching stalks or stipes,
very much after the manner of the leaves on the ends of the twigs of a

tree, the sporangia lie in a direction parallel to the empty parent frustules

452 PHYSICAL GEOGRAPHY,

by which they have been generated, instead of across them, as is the case
in £:pithemia, Although in many cases the frustules, which are about to
conjugate and form sporangia, split into two separate parts, so that their
contents may freely coalesce, we find that there are examples where the
valves only split apart at one end to a slight extent, but enough to serve
for the escape of the endochrome. Instead, also, of the pair of conju-
gated frustules, producing between them two sporangia, they may develop
but a single one. The Jelosire and Biddulphie (the former looking like
a string of pill-boxes attached together by their tops and bottoms; and
the latter being somewhat like a number of wool-sacks united at the cor-
ners into a chain), Mr. Thwaites remarks, “would seem in their develop-
ment of sporangia to offer an exception to most diatomacez; for, in those
genera, no evident conjugation has been seen. However, something anal-
ogous to it must take place; for, excepting the mixture of endochromes
of two cells, the phenomena are of precisely similar character. Thus,
instead of the conjugation of two frustules, a change takes place in the
endochrome of a single frustule; that is, a disturbance of its previous
arrangement, a moving towards the centre of the frustule, and a rapid
increase in its quantity; subsequently to this it becomes a sporangium.
In a single cell, therefore, a process, physiologically precisely similar to
that occurring between two conjugating cells, takes place; and it is not
difficult to believe, taking into view the secondary character of cell-
membrane, that the two kinds of endochrome may be developed at the
opposite ends of one frustule as easily as in two contiguous frustules,
and give rise to the same phenomena as ordinary conjugation.” In such
genera as have their siliceous frustules enclosed within membranous
tubes, as Schizonema, conjugation seems to take place both without and
within the tube, but oftenest upon the outside. As has been remarked,
“one reason for the paucity of observations on this process in the dia-
tomacez is no doubt to be found in the changes which usually take place
in the condition of these organisms at this period of their existence.
During conjugation the process of self-division is arrested, the general
mucus envelope or stratum, produced during self-division, is dissolved,
and the conjugating pair of frustules become detached from the original
mass; they are thus more readily borne away and dispersed by the sur-
rounding currents, or the movements of worms and insects, and their

NATURAL HISTORY OF THE DIATOMACEZ. 453

detection becomes in consequence more casual and difficult.” The
modes of conjugation have been reduced to four classes, thus: Ist. We
have two parent frustules and two sporangia, as the result of their con-
jugation. This mode has been seen to take place in the genera Epzth-
emia, Cocconema, Gomphonema, Encyonema, and Colletonema. 2d. From
the conjugation of two parent frustules we have formed a single sporan-
gium. This mode has been only seen to take place in Hzmantidium, but
most likely will be found hereafter to be natural in allied forms. 3d.
The valves of a single frustule separate, the contents set free, rapidly
increase in bulk, and finally become condensed into a single sporangium.
This has been seen in Cocconeis, Cyclotella, Melosira, Orthosira, and
Schizonema. 4th. From a single frustule, as in the last mode, two spo-
rangia are produced in the process of conjugation. This takes place in
Achnanthidium and Rhabdonema. Thus far has observation gone; but
no one seems to have traced the further history of the sporangium. For
we find no record of the undoubted production of gonidia, as they are
called, or seeds possessed of motion, from the contents of the sporan-
gium. In fact, we have no proof that such contents are developed into
spores, still or motile. It is true that Rabenhorst, a German observer,
has figured and described what he supposes to be the development of
gonidia or motile spores from the contents of a sporangium in a filament
of Melosira varians, an extremely common species found growing in
fresh water in all quarters of the globe. It would seem strange, there-
fore, that others have not seen the same thing; and later observers have
doubted his record for this reason alone, apparently, that they have not
chanced to see it. However, Smith, one of the best of the English
authorities on this subject, says,—‘On the whole, the facts at present
within our knowledge seem fully to warrant the conclusions that the
conjugated state of the diatomacez is the first step in the reproduction
process of these organisms; and that the sporangial products of this
condition become the parents of numerous young frustules destined to
renew the cycle of phenomena which accompanies the life and growth of
the species from which the sporangia have thence originated.” It is very
likely that the contents of the sporangium are converted into spores or
gonidia, as Rabenhorst has stated, and that after escaping and moving
rapidly about, and thus aiding in distributing the species, these gonidia

454 PHYSICAL GEOGRAPHY.

develop around themselves siliceous shells or skeletons, and become dia-
toms of the normal dimensions of the species from and by which the
sporangium was produced. On the other hand, the sporangia may con-
stitute the “resting” state, such as is known to occur in several simple
forms of life, in which the species encounters the severity of the winter
only to reproduce the species in the spring. In this case, examination of
localities, known to produce certain species during the summer, should,
during the winter months, be searched when most likely there would be
found abundance of sporangial forms. I am not aware that any such
investigations have been as yet made; and the difficulties surrounding
the study of these organisms is so great that but few have the patience
requisite for such work. Hence we find that most of the papers relating
to the diatomaceze, which have been published, are by persons who de-
light in the naming of “new species,” and have not cared to spend the
time necessary to determine whether they be but transition forms, spo-
rangia, or true species.

Although, then, as has been said, the whole life-history of the diato-
maceous sporangium has not been established, yet we know enough to
convince us, as Prof. Smith says, that “the ordinary diatomaceous frus-
tule seems to owe its production to the protoplasmic contents of the
sporangial frustule formed by the process of conjugation. These spo-
rangia, like the seeds of higher plants, often remain for a long period
dormant, and are borne about by currents, or become imbedded in the
mud of the waters in which they have been produced, until the circum-
stances necessary to their development concur to call them into activity.
At such times, their siliceous epiderms open to permit the escape of
the contained endochrome, which is resolved into a myriad of embryonic
frustules; these either remain free, or surround themselves with mucus,
forming a pellicle or stratum, and, in a definite but unascertained period,
reach the mature form of the ordinary frustule.” Prof. Smith has made
observations which appear to establish this fact of the formation of
motile spores, which he details in the following words: “In the gathering
of Cocconema Cistula, made in April, 1852, which contained numerous
instances of the conjugating process, I observed the frequent occurrence
of cysts enclosing minute bodies, variable in their number and size, and

many of which had the outline and markings of the surrounding forms,

NATURAL HISTORY OF THE DIATOMACE. 455

and were obviously young frustules of the Cocconema. It would appear
that production of the young frustules is preceded by the separation and
throwing off of the siliceous valves of the sporangium, and the constric-
tion or enlargement of its primordial utricle, according to the number of
young frustules originating in its protoplasmic contents. In this gather-
ing, forms of every size, intermediate between the minutest frustule in
the cyst and the ordinary frustules engaged in the conjugating, were
easily to be detected; and the conclusion was inevitable that the cysts
and their contents were sporangia of the species with which they were
associated, and indicated the several stages of the reproductive process.”
Although this observation seems to confirm the supposition that the con-
tents of the sporangium must divide into a number of small frustules
similar to the parents from which the sporangium sprung, yet further
study is necessary before we can consider this fact established; and such
study can only be carried out by those who are willing to keep alive for
hours, days, or even weeks, such forms as they may meet with, and
spend hours at a time at the microscope, watching any change that may
take place in them.

Thus do we see the diatomaceous frustule becoming gradually smaller
and smaller, through the carrying on of the process of self-division, and
its return to the normal dimensions through conjugation, or the forma-
tion of gigantic sporangia, whose cell-contents shall return by subdivi-
sion, and the genesis of motile spores to the size of the parent frustules.
A perfect cycle of changes would seem to be thus kept up, such as is by
no means uncommon in the life-history of many simple plants grouped
under the head Protophyta. And we are at the same time reminded,
when witnessing these changes and transformations, of the equally won-
derful metamorphoses, well known to naturalists, to take place in the
jelly-fish and hydroids of our coast, or those of the insect world, and
which we see going on day by day around us. The egg becomes a grub,
the grub a caterpillar, which, in turn, changes into the quiescent chrys-
alis, in which commonly the winter is passed, only to burst forth, as soon
as the revivifying rays of the spring sun warm it into being, as the gor-
geously tinted and active butterfly, the parent of innumerable eggs,

which shall in turn produce another generation of grubs.

456 PHYSICAL GEOGRAPHY.

PAR? PELE TH,
Mopes oF OccuRRENCE, AND Uses To MAN or THE DIATOMACE-®.

And now it will be desirable to say something with regard to the
various modes of occurrence of the diatomacez, specifying the particu-
lar habitats or kinds of situations or water (salt, fresh, or brackish), for
the use of such as may wish to know more concerning these beautiful
atomies than can be told within the limits of a short sketch like the
present. Thereafter it will be well to say something of the importance
to the geologist of knowing the life-history of the diatomacez, and,
finally, their uses to man in the arts and otherwise, as they occur in
mass in various parts of the world. And in this connection we are
reminded of the words of the poet, who says,—

Naught so vile that on this earth doth live,
But to the earth some special good doth give;

for we find that the diatomacez have in past ages played, and, in truth,
still are playing, a most important part in the grand drama of nature;
and their minute dimensions is no excuse for the neglect to which they
have been subjected by scientific and capable observers.

Diatomaceze are to be looked for in both fresh and salt water, as well
as in that which can be included under neither of these heads, the brack-
ish water of seaside marshes, where the springs of to-day are overflowed
by the rising tide of to-morrow. In general, the piece of water in which
they are looked for must be permanent, for authors tell us that it is use-
less to expect to find them in the transient pools left by the rain. This
is, however, not strictly the case, for, on one occasion, I found diatoms in
a pool formed by the drainings of a stable-yard, and even little collec-
tions of water only two or three days old have occasionally yielded forms
when carefully searched, but in such cases they were only few and mi-
nute. Prof. Gregory found them in moist earth about the roots of plants,
and others have collected them from between the branches of mosses
which clustered upon tree barks or house-tops. Even the dust which
has fallen upon the sails and decks of vessels, far out at sea, have been
found to contain them, by the German microscopist, Ehrenberg, who
therefrom has deduced certain supposed facts with regard to atmospheric

NATURAL HISTORY OF THE DIATOMAECE, 457

currents. Upon these foundations Maury has formed theories which,
however true they may be in themselves, are not borne out by later
researches, for the forms which Ehrenberg supposed to be peculiar to
certain quarters of the globe have been found to be almost universally
distributed; and, therefore, any deductions, which may have been estab-
lished in consequence of their appearance upon a ship, do not prove that
they were brought from the spot where they were first seen. In fact,
the diatomaceze would seem to be more widely distributed than any other
group of organisms, animal or vegetable; and the student of them need
never be at a loss for specimens to examine. The pool by the road-side,
the mud of the river bank, the moss upon the house-top, the earth be-
neath his feet, or the air above his head, may %e searched, and will all of
them yield him material for observation, wonder, and delight. In the
living state, and, as often found, floating upon the surface of the water
of a pond or slowly running river, swamp, or ditch, the diatoms present
themselves as a flocculent collection of more or less dark rust-colored
matter, coherent in stringy masses, when such genera as Melostva, Frag-
tlaria, or Himantidium occur, or consisting of particles readily dispersed
and scattered when Wavicula, Pinnularia, or other so-called free genera
exist. The color of such a mass may vary from a golden orange to a
dark brown, according to the thickness of the stratum or particular spe-
cies present, or, it may take on a greenish tinge at certain seasons, which
is supposed to indicate a change in the character of the endochrome
having some connection with the process of reproduction. At times, I
have found that bright green masses of floating conferva,—which are
filamentous water-plants found in all waters, both fresh and salt,—will
yield beautiful specimens of diatoms, which are entangled among their
branches, or grow adherent to them. But in most of such cases the
species belong to the group of adherent forms, and for those we are to
look to submerged plants, sticks, metal, and stones, and there they
appear as a brownish or fawn-colored mass, either closely adherent, or
with its free ends floating freely in the water, as delicate threads, borne
hither and thither by the changes of the current. A sprig of some
submerged plant, bearing a cluster of some such genus as /Zzman-
tidium, Frragilaria, or Tabellaria, presents a beautiful object, as the fine

hair-like filaments spread out on all sides, or bend with the motion of the
VOL. I. 60

458 PHYSICAL GEOGRAPHY.

containing water. A very little practice will enable the searcher after
diatoms to distinguish them, or to choose localities likely to yield them.
I have found that, if the adherent mud on the submerged wood-work of
a bridge or pier be scraped off and transferred to a bottle with some
water, and, when brought home, be placed in a saucer or plate, covered
with the water and exposed to the diffused sunlight which comes in at a
south window, many very beautiful forms may be procured in sufficient
quantity for observation; and, besides, in such saucers the diatoms may
be kept and grown for a length of time, and many points in their econ-
omy studied with facility. Thus they may be watched through the
process of growth by subdivision and conjugation, and the changes
which they then undergo’ observed without being under the necessity
of making several visits to their native localities to make collections.
The dead skeletons of many rare species are to be found in the muds of
our tidal rivers and harbors, that from some of our southern streams
especially, where the summer season of vigorous growth lasts longer
than with us, having yielded forms not otherwise procurable. All algae,
as the water-plants which do not bear apparent flowers are called, both
marine and fresh water, bear upon their fronds diatoms in greater or less
numbers; and the results of dredgings in deep water will provide the
student with ample material for many an hour’s amusement and instruc-
tion. The various methods to be employed, in preparing clean or mixed
gatherings of diatomaceze, can for the most part only be learned from
experience, as the books tell us little on this subject. Some general
directions, however, on this point will be appropriate to this sketch, and
will be given hereafter. As the diatomacez live, grow, and multiply,
thus floating freely on the surface, along the bottom, or through the
mass of the water, or wave in tiny filaments from other objects, they
must die; and the most perishable part of their bodies, namely, the cell-
contents, will be dissolved in the water or dissipated in gases, to return
and again build up new individuals at some future time. But their less
perishable portions, their siliceous skeletons, will fall to the bottom of
the pond, lake, ocean, or river, and there collect. Their remains will
also be found in the stomachs of such animals as are vegetable feeders,
as are most of the mollusca, like the oyster, the clam, and the water
snails, as well as the crustacea,—lobsters, crabs, and the like. So, like-

NATURAL HISTORY OF THE DIATOMACE., 459

wise, the alimentary canals of sea urchins and sea cucumbers, as they
are commonly called, but whose correct and scientific, although, perhaps,
at first more incomprehensible names are echinoderms and _ holothurians,
as well as many fish and countless smaller creatures inhabiting the
waters, both fresh and salt, will be found to contain the skeletons of
diatoms which they take in directly as food, or indirectly when browsing
upon the algze and other examples of aquatic vegetation. So the exami-
nation of the half-digested food, from the stomachs of these creatures,
will often repay the trouble of preparing it for the microscope. And
here is an appropriate opportunity of saying something with regard to
that remarkable and important substance which goes by the name of
guano, and which has proved to be an almost inexhaustible storehouse
for beautiful forms of diatomacez. Very generally this substance is
supposed to be the excrements of birds, which has accumulated in large
quantities during the lapse of many years upon the rocky islands in the
Pacific ocean and elsewhere, in latitudes where little or no rain falls to
wash out the organic matter. This substance has been used by the
inhabitants of the coast of South America from time immemorial as a
manure ; and, since it was introduced into Europe by Humboldt, in 1804,
it has been largely exported to that country and this, to supply the
exhaustion of our fields by the continuous crops necessitated by our
always increasing population.

Some years since, the attention of the writer of this sketch was called
to the subject of guano, when engaged as an analytical chemist in exam-
ining fertilizers of different kinds; and thereafter, when studying the
diatomacez and the application of a knowledge of them to geology, he
pushed his investigations still further, and at last came to the conclusion
that the popular prevalent notion with regard to the origin of guano was
erroneous. His ideas on the subject he embodied in a communication
made to the Essex Institute of Salem, Mass., on the 4th of January,
1869, an abstract of which will be found in the Bulletin of the Associa-
tion, vol. I, p. 11. Subsequently, with the Hon. E. G. Squier and Dr.
A. Habel, who had visited the celebrated Chincha islands, and there
observed some facts which confirmed the present writer's notions with
regard to it, he again brought the subject prominently before the public
at a meeting of the New York Lyceum of Natural History, held May 1,

400 PHYSICAL GEOGRAPHY.

1871. (Proceedings Lyc. Nat. Hist. N. Y., vol. I, p. 224.) Therein it is
shown that guano is most likely not the excrements of birds or other
similar animals, deposited upon the islands and main land after their
upheaval, but that it is the result of the accumulation of the bodies of
animals and plants, for the most part minute, the diatomaceze making up
a large part of the mass, and subsequently upheaved from the bottom
of the ocean by volcanic agency, which is known to be very active and
pretty constant in that part of the world. In this way guano has
become a storehouse of many otherwise rare and beautiful forms of
diatomacez, which can be procured from it by employing a proper pro-
cess with chemicals to destroy and remove everything but the siliceous
skeletons, which are then left in all their purity, so that their forms
may be viewed by means of the microscope. The process for cleaning
guano, so as to obtain the microscopic organisms contained in it, will
be described hereafter.

In a semi-fossil condition, the diatomacez are to be found in all parts
of the world, and very extensively within the state of New Hampshire
in the form of what have been called lacustrine sedimentary deposits,—
that is to say, collections of their dead skeletons formed at the bottom
of lakes, and going commonly by the name of “marl,” although true marl
contains few, if any, diatoms, and is largely made up of the shells of
mollusca, snails, and the like. The mode of formation of these deposits
will be described hereafter.

Still more ancient, and, what may be with propriety termed truly fossil
deposits of fresh-water diatomacez, are not found on this coast of the
North American continent, but, in fact, appear to be confined to the
Pacific states, where they cover vast tracts of country. Their mode of
formation will be described when we come to treat of the application of
a knowledge of the diatomacez to geology, in a subsequent part of this
sketch. Thus extensive strata of diatomaceze have accumulated and
become fossilized, and constitute the “infusorial earths” of geologists
and others, many of those on our Pacific coast, as has been said, being
made up of the remains of fresh-water species which have lived, grown,
died, and been laid up in countless millions in the beds of now extinct
lakes; while, likewise, in California, as well as in Virginia and Maryland,

in Peru, Japan, and Algeria, are found layers which are made up of the

NATURAL HISTORY OF THE DIATOMACEZE, 461

skeletons of marine species. The city of Richmond, Va., rests upon
such a stratum, which varies in thickness from twelve to twenty-five feet,
and which extends to Fortress Monroe and over the Potomac river into
Maryland, and all the way down on both sides of the Patuxent river in
that state. The principal localities from which these deposits, fresh-
water and salt-, have been obtained so far, will be mentioned in the
directions for collecting, to be given hereafter.

Besides objects of great beauty and scientific interest, the uses to
which the diatomaceze have been put may be briefly summarized. It
is to be hoped that the unlearned, whose attention has for the first time,
perhaps, been called to them by this sketch, will feel that the elegance
of their forms and the geometrical purity of their sculpture will recom-
mend them sufficiently, without eliciting the question, which unfortu-
nately has been propounded with reference to other scientific subjects,
viz, What good are they? That they serve as food for numerous
aquatic animals is plainly shown by the fact of their being found in
their stomachs; but, if that were their only use, it could hardly be
said that they were of value to man directly. Who would suppose
that these little atomies, so seemingly insignificant, could serve as sus-
tenance for the human race?—and yet such is the fact. In the bleak
and almost barren parts of Lapland, during times of scarcity from failure
of the crops, the infusorial deposits are turned to account, under the
name of “berg-mehl” or mountain meal, to eke out the scanty supply of
flour with which they are mixed before it is made up into bread and
eaten. In some other parts of the world we find wild nations making a
similar use of such “infusorial deposits ;” but we can hardly say they
serve as food, for although some authors have supposed that some of the
organic matter they contain may be absorbed by the stomach or intes-
tines, it is not likely that such is the case. It is much more probable
that the earthy material serves to clog the stomach, and, by the mere act
of distention, arrest for a time the pangs of hunger. Their siliceous
character is opposed to their serving as food in the true acceptation of
that word. In Samarancy and Java, under the name of “tanah,” an
earth of this kind, made up of the siliceous remains of diatomaceze, is
eaten. It is described as “generally solid, plastic, and sticky, and is
rolled and dried in the shape of small sticks over a charcoal fire, and is

462 PHYSICAL GEOGRAPHY.

eaten as a delicacy.” The natives of our western coast, as well as the
inhabitants of some parts of South America, use an “infusorial earth” as
a pigment to decorate their bodies. In guano, doubtless the diatomaceze
play a very important part, when that substance is employed as a fertil-
izer and spread upon our fields, for they then present the silica in an
extremely minute state of division to the moisture of the soil and the air,
which gains admittance thereto, either along with the water or on account
of the porosity of the earth. It has been found that under these circum-
stances the silica is dissolved and absorbed by the plant that requires it,
in whose tissues it is deposited to form a strong support to its frame-
work. The cereals especially require a certain amount of silica, as is
well known, for the strengthening of the stem which serves to elevate
the seed where it gets the benefit of the sun and the air. So we find
that all the grasses, as wheat, oats, sugar-cane, maize, grow best on a
soil from which they can abstract sufficient silica for the purpose indi-
cated. Instances have come to my knowledge where recent wet deposits
of diatomacez, especially those containing organic matter, and men-
tioned above under the designation of lacustrine sedimentary, have
proved of real value as fertilizers, when mixed with stable manure and
used for cereals, but, of course, they would be objectionable if applied
to root, fruit, or leaf crops.

Many deposits. of diatomacez are called tripoli and polishing pow-
ders; and these names indicate that they are possessed of properties
which peculiarly fit them for polishing hard surfaces, such as metal.
The extremely minute state of division of the silica in the diatom-valves,
and the readiness with which those valves are fractured and broken down
into still smaller angular portions, are remarkable, and could hardly be
imitated by any artificially prepared powder. It has been suggested that
the vast diatomaceous deposits found in some parts of the world, as the
strata occurring in Virginia and California, might be turned to account,
as presenting silica in a fine state of division, so that it can readily be
acted upon by the alkali, and the so-called “soluble glass” made there-
from. One manufacturer has experimented somewhat in this direction,
but with what result is at present unknown.

It is, however, to the scientific student that the diatomacez are of the
greatest interest and really of use, for they have proved valuable in

NATURAL HISTORY OF THE DIATOMACEZ. 463

assisting him in the investigation of various subjects, as the matter of the
conditions of existence of the simple cell, and, likewise, the former char-
acters of certain strata in which they are found in vast numbers. The
bearings of this latter subject will occupy our attention in Part Sixth.

PAR. Oho fis
Tue DIATOMACE AND GEOLOGY.

The manner in which the diatomacez increase, both by true growth
and reproduction, has been described in such detail that it is to be hoped
that it is thoroughly understood. At the same time, it can be readily
comprehended how, as they secrete, from its solution in the water in
which they live, the siliceous material constituting their harder parts,
and, as they die, this flinty matter must after a time form a deposit at
the bottom of the lake or ocean which they inhabit. We are, then, pre-
pared to take into consideration the formation of such deposits, both
fresh and salt, and their connection with the science of geology.

The mode of formation of fresh-water deposits of diatomacez, as
lacustrine sedimentary strata and as fluviatile fossil layers, has been
fully described in a paper read by the present writer before the New
York Lyceum of Natural History, Nov. 28, 1870, and published in the
proceedings of that association, vol. I, p. 109; and the major part of that
communication will be given here as embodying about all that is known
on that subject, and detailing at the same time the author’s ideas with
regard to the enormous deposits of fresh-water diatomaceze found spread
over many parts of the western states of the North American continent.

We have seen how the diatomacez increase by subdivision, so that by
this means alone they may multiply extremely rapidly, and a single indi-
vidual, by means of its descendants, soon populates a large pond or lake.
But while subdivision or true growth has been thus progressing, increase
by generation or seeding may have taken place at the same time, and,
from each individual in turn, several young may have been brought
forth, which would multiply the rate of increase very materially, of
course. It is true that the mode of seeding of these organisms is not
thoroughly understood; but we know enough to say that it does occur,
and very frequently, and that the number of new individuals thus formed
is very great. At the same time, numerous individuals are dying, and,

404 PHYSICAL GEOGRAPHY.

as they do so, much of the organic matter of which they are composed
is dissipated, but some of it, along with the hard siliceous valves and
connecting membranes which constituted the skeletons of the diatoms,
falls to the bottom of the pond, and forms a layer of greater or less
thickness, according to the time during which it has been accumulating.
If it be exposed now, by draining such a pond, it may appear as a brown
or grey powdery mass, but, if it has rested beneath the the water suffi-

ciently long, almost all of the organic matter will be removed, and the

clean, white siliceous skeletons alone remain. In some localities,—and
this I have found to be the case in the state of New Hampshire, perhaps
from the peculiar topography of the spots where these masses of the
accumulated dead shells of diatoms are found,—these organisms grow in
bogs of no very great superficial extent, but which, from their occurring
in hollows between hills, are often quite deep. Under such circum-
stances, as I should judge from the character of a deposit I examined at
Bowkerville in Cheshire county, the organic matter might for the most
part decay out of a layer of considerable thickness, and nothing be left
but a mass of finely divided siliceous material of a character well fitted
for use as a polishing powder, or for other purposes to which this sub-
stance has been applied.

Such are the results, then, of this rapid growth of the diatomacee in
ponds, lakes, marshes, and rivers; and, as the first examples of such
deposits which I examined were found beneath layers of peat, I gave to
them the name “sub-peat” deposits, and under that designation they
have been generally known. After a time, however, specimens came
into my hands which were procured from the bottoms of existing ponds,
and these, besides consisting for the most part of little else than silica,
and being of an almost pure white color, had no peat overlying them.
Hence, of course, I saw the inapplicability of the term “sub-peat” to
such deposits, and for them I have coined a new name, viz., lacustrine
sedimentary, which I consider more appropriate, and at the same time
indicating their usual origin, and including all deposits of fresh-water
diatomaceous remains, with the exception of certain peculiar layers to
be hereafter described. Of course the sub-peat then become a variety
of these. Deposits of this character are extremely common in this
country, as well as elsewhere, and it will be at once seen that, although

NATURAL HISTORY OF THE DIATOMACE®. 4605

any one of them might be of great thickness, yet it does not necessarily
follow that it had been forming for any great number of years; and
geologists and others are not warranted, from observance of this one
fact of thickness, in supposing that a great length of time has inter-
vened during its deposition. Thus, some years since, I examined one
of these lacustrine sedimentary deposits, at a spot near the town of East
Stoughton in Massachusetts, which was fully twelve feet thick, but only
covered a few feet of surface, which circumstance was due to the occur-
rence of a dam across the course of a stream, which arrested its progress
and formed a small, deep pond, into which all of the diatomacez, which
grew for some considerable distance up stream, drained, and, dying,
accumulated as a light grey-colored powder. I have received specimens
of similar material from many points in this country, so that about one
hundred have been examined. The state of New Hampshire has sup-
plied quite a number, and they will be hereafter described, and the
forms detected in them illustrated.

The first recorded discovery of a lacustrine sedimentary deposit of
diatomacez in this country is found in Sz//:man’s Fournal, 1839, vol.
xxv, p. 118, in an article “On Fossil Infusoria discovered in Peat-earth
at West Point, N. Y., with some notices of American species of Dia-
tome. By J. W. Bailey.” Of this I have a small portion given me by
Prof. Bailey himself, and, on examination, it is found to have the general
characteristics of these deposits; that is to say, it is of a grey color,
light in density and very friable, and is made up of the siliceous skele-
tons of such species of diatomacez as grow in small fresh-water lakes,
ponds, and marshes. In fact, Prof. Bailey says that this deposit, which
was “eight or ten inches thick, and probably several hundred square
yards in extent,” was discovered “about a foot below the surface of a
small peat-bog immediately at the foot of the southern escarpment of
the hill on which the celebrated Fort Putnam stands.” He considers
the remains present in this stratum to be “in a fossil state.” And here,
perhaps, it is desirable to say something with regard to the use of this
term. Its origin would warrant its being applied to anything dug up out
of the earth; and, as Mr. Page remarks in his Handbook of Geological
Terms, “hence the earlier geologists spoke of ative fossz/s or minerals,

and ertrancous fossils, or the bodies of plants and animals accidentally
VOL. Ot

466 PHYSICAL GEOGRAPHY.

buried in the earth.” For myself, I am disposed to restrict the term
fossil to the remains, more or less perfect, of organized beings dating
anterior to the present epoch, if we can conscientiously speak of epochs
at all where the progression and rate of change have been so gradual.
Considered thus, then, these remains of diatomacez cannot be classed
as fossils; and at once the geologist perceives that they are to be taken
into account in a very different manner from what they have been hith-
erto. So much, then, for lacustrine sedimentary deposits of diatomacez ;
and I trust that I have made clear as to what they are, and how they are
formed and forming. At the time I made his acquaintance, Prof. Bailey
expressed an opinion that similar strata would be found beneath every
bog and pond in the country. The clear scientific vision of my late
friend is evidenced in the fact that this prediction was proved almost lit-
erally true. I have over one hundred such specimens, and am continually
receiving others. Several I have already described, and others remain to
be examined, and facts with regard to the geographical distribution and
other points will be elucidated by such investigations,—so that I am
always anxious to receive contributions from all sources. It is only
desirable that all facts connected with their mode of occurrence, as to
amount in thickness and extent, over- and underlying material, etc., be
noted at the time of making the gathering.

We now come to consider deposits of an entirely different character
from those just spoken of, but which yet are also made up almost en-
tirely of the siliceous remains of fresh-water diatomaceze. These are
the so-called “infusorial” deposits found in such enormous quantity in
our Pacific states. From time to time, during the last thirty years, spec-
imens of these have come into the hands of naturalists, from collectors
and otherwise, and also “in place” they are well known to settlers in the
districts where they occur. As their true character has not been under-
stood, they have received various appellations, as “magnesia,” “porcelain
clay,” “white clay,” “chalk,” “siliceous marl,” “ microphytal earth,” “trip-
oli,” “rotten-stone,” “pipe-clay” or simply “clay,” “trachytal tufa,” and
“phytolitharian tuff,” by Ehrenberg. These specimens are almost always
white in color, or nearly so, although there are records of some strata

occurring of various tints. None of these except the white ones have
come under my observation, so I am not prepared to state that the

NATURAL HISTORY OF THE DIATOMACEZE. 467

colored ones are diatomaceous. Besides, this material is of a somewhat
hard, stony character, but porous withal, and light; as a general thing,
also, it is readily broken, but not easily powdered, as are the lacustrine
sedimentary deposits. On account of this hardness there is found to be
considerable difficulty in preparing these specimens for microscopical
examination. After so preparing, by a method I have devised, to be
described hereafter, and viewing with a sufficiently high magnifying lens,
this substance is found to be made up entirely of the siliceous remains
of fresh-water diatomaceze which have been matted together in the re-
markable manner described. The species of diatomacez present, how-
ever, are found to be very different in character from those to be seen in
the other class of recently formed deposits. Thus, while the genera
most commonly represented in and making up the mass of the lacustrine
sedimentary deposits are Vavicula, Pinnularia, Stauronets, Synedra, and
similar elongated forms, the hard, white material is in general found to
consist of myriads of examples of Orthosira, Cyclotella, and similar dis-
coid forms. Although our knowledge of the forms of these minute
organisms, peculiar to different kinds of collections of water, is rather
imperfect, yet we know that the naviculeform genera spoken of above
are found in small lakes, while in the larger pieces of water are to be
seen growing more particularly the discoid genera like Cyc/otella. From
this fact alone, then, we should be prepared to assume that the waters,
in which the organisms whose remains make up these deposits grew at
one time, covered large tracts of country. And our surmises on this
point are confirmed by the reports of explorers who have passed over
this section of country, that is to say, on both sides of the Sierra Ne-
vada Mountains, from Puget’s sound to the southernmost border of
California, for they tell us that these deposits extend over a consider-
able portion of the Pacific states.

I have examined many specimens from this district, and, on account
of the mode of occurrence of this material, being capped by lava, basalt,
or some volcanically-erupted rock, I have designated them sub-plutonic.
The first specimens of such sub-plutonic deposits of diatomacez, which
were put into the hands of scientists, were undoubtedly those brought
home by Frémont, from his expeditions to the Rocky Mountains, in
the year 1842, and to Oregon and North California, in the years 1843

468 PHYSICAL GEOGRAPHY.

and 1844. The discovery of these, as detailed in his report, gives a
good idea of this portion of the country, and is as follows. It must be
premised that, in that report, what is now known as the Des Chutes
river, and which is one of the tributaries of the Columbia, is called
“Fall river” (Riviere aux Chutes); so, also, he spells Klamath lake
“Tlamatt.” Speaking of the tributaries of the Columbia river, he says
(p. 200),—

These streams are characterized by the narrow and chasm-like valleys in which they
run, generally sunk a thousand feet below the plain. At the verge of this plain they
frequently commence in vertical precipices of basaltic rock, and which leave only
casual places at which they can be entered by horses. The road across the country,
which would otherwise be very good, is rendered impracticable for wagons by these
streams. At such places the gun-carriage was unlimbered, and separately descended
by hand. Continuing a few miles up the left bank of the river, we encamped early in
an open bottom among the pines, a short distance below a lodge of Indians. Here,
along the river bluffs present, escarpments seven or eight hundred feet in height, con-
taining strata of a very fine porcelain clay, overlaid, at the height of about five hundred
feet, by a massive stratum of basalt one hundred feet in thickness, which again is suc-
ceeded above by other strata of volcanic rocks. ‘The clay strata are variously colored,
some of them very nearly as white as chalk, and very fine grained. Specimens
brought from there have been subjected to microscopical examination by Prof. Bailey,
of West Point, and are considered by him to constitute one of the most remarkable
deposits of fluviatile infusoria on record. While they abound in genera and species
which are common in fresh water, but which rarely thrive where the water is brackish,
not one decidedly marine form is to be found among them; and their fresh-water
origin is therefore beyond a doubt. It is equally certain that they lived and died in
the situation where they were found, as they could scarcely have been transported by
running waters without an admixture of muddy particles, from which, however, they
are remarkably free. Fossil infusoria of a fresh-water origin had been previously de-
tected by Mr. Bailey in specimens brought by Mr. James D. Dana from the tertiary
formation of Oregon. Most of the species in those specimens differed so much from
those now living and known, that he was led to infer that they might belong to extinct
species, and considered them also as affording proof of an alternation, in the forma-
tion from which they were obtained, of fresh- and salt-water deposits, which, common
enough in Europe, had not hitherto been noticed in the United States. Coming evi-
dently from a locality entirely different, our specimens show very few species in com-
mon with those brought by Mr. Dana, but bear a much closer resemblance to those
inhabiting the north-eastern states. It is possible that they are from a more recent
deposit; but the presence of a few remarkable forms, which are common to the two
localities, renders it more probable that there is no great difference in their ages.

NATURAL HISTORY OF THE DIATOMACE/E. 469

I have given in full all that Frémont says regarding this locality, as it
presents us with the first discovery of strata of the remarkable character
of which I am now treating, and is therefore of special interest. Bailey’s
report, contained in the same volume, merely mentions and figures the
principal forms he detected.

The only other description of this locality and these remarkable
deposits, fortunately, is a much more complete and scientific one. It is
that of Dr. J. S. Newberry, as geologist of the expedition under Lieuts.
R. S. Williamson and Henry L. Abbot, which explored the route for a
railroad, from the Sacramento valley to the Columbia river, in 1855,
and will be found in vol. vi of the Pacific Railroad Survey Report. Dr.
Newberry gives a description of the geology of the Des Chutes basin,
which is essentially as follows. It must be remembered that the Des
Chutes and Fall river, mentioned above, are one and the same. The
Des Chutes basin consists of a series of plateaus, having varying eleva-
tions from four thousand to twenty-two thousand feet above the level of
the sea, separated by subordinate ranges of volcanic mountains. These
plateaus are usually covered by a floor of trap, which extends in a
smooth sheet from fifty to a hundred and fifty feet in thickness, un-
broken except by and at the cafions of the various streams which, as a
general thing, flow from the interior to the ocean at right angles to the
coast line. Beneath this bed of trap is the whitish or light-colored
material, consisting of the siliceous remains of diatomacez we are con-
sidering, sometimes occurring as a single bed only, sometimes as a series
of beds locally intercalated with thin beds of trap. These infusorial
strata, as they have been called, are cut in many places by the Des
Chutes and its tributaries to the depth of more than a thousand feet,
without exposing the basis on which they rest. They are usually quite
horizontal, from a few lines to twenty feet in thickness, and very accu-
rately stratified.

Psuc-see-que creek, one of the tributaries of the Des Chutes river,
flows through a valley of a remarkable character, as its sides consist of
several alternate strata of diatomaceous material and columnar trap or
concrete. Near the base of this series of layers is a stratum, three feet
in thickness, of brilliant white feldspathic pumice, so soft as to be easily
crumbled in the fingers. Above, and lying upon this, is a line of dark

470 PHYSICAL GEOGRAPHY.

carbonaceous matter, less than a quarter of an inch in thickness, from
which, up into another layer of pumice, projects the remains of the
branches of some small plant which had apparently been killed by the
overflow of the pumice. Lieut. Williamson gives a striking view of this
locality, and speaks of it in the following terms:

This river cafion is very remarkable. Its sides vary from eight hundred to two thou-
sand feet in height. The river has cut down its bed to this immense depth through
successive strata of basalt, with occasionally a deposit of infusorial marl and volcanic
tufa, which has sometimes hardened into a kind of conglomerate sandstone ten or
twenty feet in thickness, and of a white, grey, or reddish color. We followed down
this cafion for about five miles, when a rocky spur cut off all further progress, and
compelled us to attempt the ascent. This with great difficulty we accomplished, and
found ourselves on a plain thinly dotted with sage bushes and clumps of grass. We
continued our course, and, after crossing the bed of a torrent of the rainy season,
came to a very small stream, called Psuc-see-que by the Indians. It was sunk in a
cafion about five hundred feet deep, cut through successive strata of basalt, infusorial
marl, tufas, and conglomerate sandstone like that found in the Mpto-ly-as cafion (pp.
84, 85).

Another locality in which these remarkable deposits occur is on the
Pitt river; and Lieut. Williamson’s description gives such a good idea

of the mode of their occurrence that I transcribe it, also, below:

The banks of the Pitt river, both above and below the mouth of Canoe creek, are
partially formed by regularly stratified sedimentary deposits, the first seen since leav-
ing the valley of the Sacramento. They appear on both sides of Pitt river at intervals
for several miles, being in many places interrupted or covered by beds of trap. They
are, perhaps, best exposed in the cafion formed by the passage of the river through
««Stoneman’s ridge,” the most conspicuous of the lines of upheaval which form what
is known as the lower cafion of Pitt river. They here exhibit a thickness of about
fifty feet, but are considerably tilted up, and are covered by a thick bed of trap which
has been poured out over them. They exhibit narrow and parallel lines of deposition,
but are very homogeneous, and can hardly be said to form more than two distinct
beds. Of these, the upper is white, resembling very pure kaolin, derived from the
decomposition of crystalline feldspar. The lower bed is light brown or dirty white in
color, and has a slightly gritty feel between the fingers. These strata rest upon a
thick bed of rolled and rounded fragments of traps, porphyry, and basalt of all sizes,
from masses of two and even three feet in diameter, to pebbles. They are generally
as large as one’s head, and great numbers are each a foot in diameter. The surface
of this bed of boulders is perhaps twenty feet above the present surface of the stream ;
but it bears indubitable evidence of having at one time been covered by it, or, at least,

NATURAL HISTORY OF THE DIATOMACEE, 4

the stones composing it, so large and clear, have been rounded where they lie by a
current or waves of water. The appearance presented by this bed of boulders is dif-
ferent from that of any of the beds of volcanic conglomerate which are so common in
many parts of California and Oregon, or of the stratified conglomerates of the Sacra-
mento valley, and it is undoubtedly of local origin. The trap which formed the
greater part of the bank above is evidently of recent date, more recent than the infu-
sorial marls, and the marls more recent than the conglomerate, and the conglomerate
an accumulation of rolled stones and pebbles, which belongs to the present epoch.
The trap which overlies the infusorial marls composes a large part of the walls of the
cafion at this point, where it has been cut away by the stream, and forms nearly per-
pendicular faces of several hundred feet in height. The soft nature of the underlying

strata has, however, very much assisted in its removal (p. 33)-

There are several localities besides those mentioned at which this,—
what I have chosen to designate “sub-plutonic,’—material is found, as
at Klamath lake, on the northern border of California, and elsewhere all
through the Pacific states. From these I have received gatherings, and
have thus been enabled to examine, by means of the microscope, spec-
imens from many points in what was once this chain of enormous
fresh-water inland seas,—for such they deserve to be styled. For as the
microscope reveals the fact, the organisms, whose stony remains consti-
tute the mass of these deposits, were inhabitants of collections of fresh
water which existed at some past period as large lakes; and a careful
geographical examination of the country enables us even to indicate, to
a certain extent, the situations once occupied by these now extinct seas,
which at times varied in superficial dimensions, and certainly were in
some cases drained, overflowed by lava, and renewed and replenished
with living organisms as many as seven times.

And now that we understand how it is that lacustrine sedimentary
deposits are formed by the accumulation of the dead shells of diato-
maces, we can comprehend the manner in which these sub-plutonic
strata have been laid down. If we look at the map of the western
coast of the North American continent, we see that there are three
great chains of mountains, about parallel to each other and the coast
line, and thus enclosing between their peaks two long and wide valleys.
The Rocky Mountains are the first of these chains, and they at one
time formed the coast of this continent. Slowly and gradually, however,
there appeared a line of islands at a distance from the coast, whose

472 PHYSICAL GEOGRAPHY.

material was volcanic, and, as these islands rose higher and higher, the
space between them and the coast cliffs also rose until it became dry
Jand. Soon rain fell and accumulated in this valley so formed, and lakes
and rivers appeared. In these, diatomacez appeared, thrived, grew,
reproduced, and multiplied; lacustrine sedimentary deposits were thrown
down. Now came a time when the volcanic cones, which constituted the
peaks of the range of mountains nearest to the coast, burst forth with fire
and lava; and, probably at the same time, earthquakes took place which
drained many of the lakes and changed the courses of rivers. Into the
lake basins the lava was poured, with its heat evaporating the moisture,
and consolidating the diatomaceous material into a stony mass, from
which all organic matter was burned out. A period of rest succeeded.
Diatoms again appeared and accumulated, to be again overlaid by lava;
and so on the same thing may have again and again taken place. In
this way the enormous deposits of sub-plutonic diatomaceze were formed ;
and in the cracks, made in the rock by volcanic agency, the rivers
wended their way, and made the gates we now are in the habit of call-
ing cafions.

But in the ocean diatomaceze also occur, and in large quantities.
When they die there, their siliceous remains must accumulate at the
bottom of the water, and occur as deposits. It is in the black mud of
our quiet bays and harbors that we must look for the greatest accumu-
lation of these remains; and rivers are carrying them down to their
mouths, where often they are piled up in such masses as to form bars.
The mud of the river Thames in England yielded to Mr. Roper a large
number of diatomaceous remains. Ehrenberg examined the mud of the
Elbe in Germany, and found these minute shells to make up from one
quarter to one third of the whole mass. He calculated that at Pillau
there are annually deposited from the water from seven thousand two
hundred to fourteen thousand cubic metres of these minute shells,
which in the course of a century would give a deposit of from seven
hundred and twenty thousand to one million four hundred thousand
cubic metres of deposit, which might be hardened into a stony mass.
That such hardening has taken place is evidenced by the occurrence of
the vast strata of marine forms found in Virginia and Maryland, on the
Atlantic side of North America, and in California on the Pacific coast.

NATURAL HISTORY OF THE DIATOMACE. 473

This material is often almost white, but more commonly is tinted slightly
yellowish or salmon-colored. It makes up the most part of the material
of the coast range of mountains in California, and has also been found
in Peru, Japan, Algeria, Spain, and the West India islands. In Cali-
fornia, in the almost rainless districts, it is used for building, but gen-
erally is too friable for that purpose. The forms occurring in it are for
the most part discoid, with a few triangular ones, and, when prepared
and examined by means of the microscope, present one of the most
beautiful objects which can be so viewed.

Something has been said with regard to the origin of the substance
known as guano, and which has been so extensively used as a fertilizer ;—
but to the agricultural fraternity anything connected with this material
must prove of interest, so it is thought best to enter more fully into the
consideration of this subject on account of its important bearings, its
value to geologists, and its general attraction, evinced by the manner in
which the publications of the present writer thereon have been copied
and circulated by the periodical press.

On May 1, 1871, a discussion took place at the Lyceum of Natural
History, New York, on the subject of guano, when the Hon. E. G,
Squier exhibited a map of the Guanape islands of Peru, where guano
is found, drawings of a wooden idol and other objects discovered in the
guano, and photographs showing that that substance is distinctly strati-
fied, and not thrown down in the shape of a confused mass, as would be
the case if it were, as is usually supposed, merely the excrement of
birds and other animals deposited on rocky islands, in localities where
little or no rain falls to wash out its soluble and valuable constituents.

Dr. A. Habel, who had visited the Chincha islands for the purpose
of studying the mode of occurrence of the guano (or, as he prefers to
write it, in consonance with the mode of its pronunciation, “whuano”),
made an extended communication showing that the outer and uppermost
portion of this substance does consist of the droppings of various spe-
cies of sea-birds and mammals, mixed with the feathers and eggs of birds,
and‘bones. This layer does not at all show signs of stratification, and is
of a reddish brown color. Below this is the guano proper, which is of a
different structure, and distinctly stratified. He says that “this stratifi-

cation is so marked that even a superficial examination must convince
VoL, 1. 62

474 PHYSICAL GEOGRAPHY.

every unprejudiced person that it is the product of sedimentary for-
mation. It is made up of alternate white and yellow strata, varying
in shade and thickness. All of these strata exhibit distinctly their
inclination or dip, which varies not only on the separate islands, but in
different parts of the same island. On the middle island, for example,
the inclination or dip of the strata in one part of it does not amount to
more than five degrees, while in another part it is eight degrees, and in
a third, close to the first, fifteen degrees.” In one place strata, running
south-west and north-east, and dipping twenty degrees, rested uncon-
formably on others running north and south, and dipping only four
degrees. In all of the strata are imbedded stones of various sizes and
weight up to fifteen pounds, as well as eggs and bones. Another proof
that the guano has been deposited beneath the ocean is seen in the
various strata of sea sand underlying it, and which are also stratified, and
dip in one direction or the other.

The present writer said that he first made his hypothesis public, with
regard to guano having been deposited beneath the water of the ocean,
in 1868, at a meeting of the American Microscopical Society. In Jan-
uary, 1869, he entered more fully into a discussion of the subject before
the Essex Institute, at Salem, Mass. He said,—

I have been for the last fifteen years or more studying the so-called ‘ infusorial
deposits” of marine origin. Among the specimens thus examined are some of the
rocks or shales making up the great mass of the mountains of the coast range, which
extend down the Pacific shore from Washington territory to the borders of Lower
California, and even perhaps down as far as the southernmost extremity of that penin-
sula. These shales are usually of a light cream color, and mainly consist of the
siliceous skeletons of diatomacee and polycystina, the former being commonly con-
sidered as plants, the latter as animals. These are of extremely minute size, and
often require for their study the use of the highest magnifying powers. Many of them
prove to be indistinguishable from forms living at the present day on the California
coast. Exuding through, and often appearing at the upper portion of these rocks, to
which situation they have evidently been driven by heat, are found the petroleum, bitu-
men, and asphalt of California. Hence the state survey has conferred upon these strata
the name of bituminous shales. Along the Pacific coast, and lying parallel to it, are
islands often bearing upon their summits deposits of guano, of more or less commercial
value. In many cases the quantity has been small and soon removed ; but I am in-
formed that there are deposits of this material in that quarter of the globe still
unworked. At the same time, it must be remembered that the whole Pacific coast, of

NATURAL HISTORY OF THE DIATOMACE, 475

both North and South America, is in an almost continual state of motion, and gradual
but constant upheaval, caused, doubtless, by the action of internal chemical changes,
which make themselves markedly evident in the volcanic vents found all along the
mountains constituting the Cascades and Sierra Nevadas of North, and the Andes of
South America. There have been identified at least three former lines of rise of coast,
and still another is seen presenting its peaks in the islands, which will, at some future
day, be united in such a manner as to constitute another coast range of mountains.

If, now, we consider the bearing of these facts on the origin of the substance known
as guano, we find the following points worthy of note. Guano may be divided into
two great groups, the ammoniacal and the phosphatic ; but it is of the first mentioned,
only, that I desire to treat at the present time, and to which I wish to apply my de-
ductions. Guano is usually considered as the excrement of sea-fowl, and which has
accumulated during a long period of time,—so long, that attempts have been made to
calculate its age from its thickness. Thus Humboldt, who first made this substance
known to the Eastern hemisphere in 1804, states, that on the Chincha islands it has a
depth of fifty to sixty feet, and that the accumulation of the preceding three hundred
years has formed only a few lines of this thickness. The facts brought forward by Mr.
Squier show how difficult it is to arrive at any certain knowledge on this point, and, in
fact, show that we have no means of ascertaining the age of the guano deposits, even
if we accept the theory of their origin from the source usually ascribed to them. We
find that guano is not confined to islands only, but occurs in large quantities on the
contiguous headlands; and many ravines, extending into the interior of the country,
contain guano in smaller and larger quantities. Thus, the ravines of Lolo, Culata,
Sacramento, Animas, Morillo, Guajes, Colorado, Chucumata, and Pica are reported to
contain pure guano deposits, covered by a thick coating of sand. Neither is it found
in rainless districts only, for, as I have said, it is found on the islands off the Califor-
nia coast, which are by no means rainless; and Mr. W. H. Dall informs me that it
occurs on the Aleutian islands, where the air is almost always saturated with moisture,
and heavy rains fall during a large part of the year. With regard to the upheaval of
such coasts along which guano occurs, it is well known, from Darwin’s investigations,
that the whole Pacific coast of South America is in constant motion and upheaval, and
that on the main land near Lima, and on the adjoining island of San Lorenzo, Mr.
Darwin found proofs that the ancient bed of the sea had been raised to the height of
more than eighty feet above the water, within the human epoch, strata having been
discovered at that altitude containing pieces of cotton thread and plaited rush, together
with sea-weed and marine shells (Lyel/, Principles, 1853, p. 502).

And Darwin says,—‘‘I have convincing proofs that this part of the continent of
South America has been elevated near the coast at least from three hundred to five
hundred feet, and, in some parts, one thousand to thirteen hundred feet, since the
epoch of existing shells.” Other proofs of this fact are not wanting, but these are
sufficient for me to quote at the present time.

When the portions of guano, which are insoluble in water and acids, are examined

476 PHYSICAL GEOGRAPHY.

by means of the microscope, they are found to be made up of the skeletons of diato-
macez, polycystina, and sponges, invariably of marine origin, and sometimes identical
with those living in the adjoining ocean, and fossilized in the adjacent infusorial strata.
Also, we find that some of these forms occur in patches exactly as they grow in nature,
and as they would present themselves if they were deposited from water, and not as
they would be if they had to pass first through the alimentary canals of mollusca and
similar small animals, then through the same organs of fish and birds, in turn, as they
would have to do to get into the guano in the manner commonly supposed.

In California we have a deposit of ‘‘infusoria,”

improperly so called, accompanied
by bitumen, which bitumen, the gentlemen of the state survey believe, has been
derived from those ‘‘infusoria,” and that contiguous thereto we have guano deposits.
Now let us see if we have a similar association of facts anywhere else. At Payta, in
Peru, Dr. C. F. Winslow discovered an ‘‘infusorial” deposit almost identical in char-
acter with the California one. Near by are bitumen springs; and lying off the coast
are the guano islands of Lobos, Chincha, Guanape, and others. At Netanai, Japan,
we have extensive ‘‘infusorial” strata and bitumen; it is not recorded whether guano
occurs in that quarter. In the island of Barbadoes we have ‘‘infusorial” strata, bitu-
men, and, near by, the guano islands of the Carribean sea; and, I am informed, guano
is abundant on the small islands and rocks nearly throughout the West Indian archi-
pelago. In the island of Trinidad we have ‘‘infusorial” strata and bitumen, and, of
course, adjacent guano. At all of these localities volcanic action is evident; but we
have some localities of guano without ‘‘infusorial” strata or bitumen, as yet recorded ;
while we have the celebrated ‘‘infusorial” strata of Virginia, which, by a little stretch
of the imagination, may be supposed to be related in some way to the petroleum of
West Virginia and Pennsylvania. In Algeria we have ‘‘infusorial” strata and bitumen;
but I never heard of guano having been found near by. From all of these facts, and
others that I have collected of no less importance, derived from chemical and micro-
scopical characters, I have come to the conclusion that guano is not the excreta of
birds, deposited upon the islands and main land after their upheaval, but that it is the
result of the accumulation of the bodies of animals and plants, for the most part
minute, and belonging to the group which Haeckel has included in a new kingdom,
separate from the animal as well as the vegetable, under the name of Protista, and
subsequently upheaved from the bottom of the ocean. Subsequent chemical changes
have transformed it into guano, or, heat and pressure have so acted upon it that the
organic matter has been transformed into bitumen, while the mineral constituents are
preserved in the beautiful atomies that make up the mass of the extensive ‘‘infusorial”
strata found in various parts of the world.

The Chincha islands have been visited by a competent geologist, Mr. Kinahan, of
Dublin, and he has pointed out that they have been upheaved by volcanic action within
a recent period, geologically considered. I have found a remarkable confirmation of
my theory in a paper, read before the American Institute, New York, some years since,
by Mr. Alanson Nash, detailing the observations of a Mr. F. Nash made during a resi-

NATURAL HISTORY OF THE DIATOMACEZE. 477

dence on the Chincha islands, while engaged in the guano trade, for nearly six months.
Therein we find it stated that Mr. Nash was of opinion that guano was formed in the
way I have described ; that the anchors of vessels in that locality bring up guano from
the bottom of the ocean; that ‘the guano is (much of it) not composed of bird dung,
but is composed of the mud of the ocean;” that ‘‘the composition taken from the
islands, called guano, is stratified, and lies in the same form it did before it was lifted
up from the ocean;” that ‘‘the bottom of the ocean, on the west coast of Peru, con-
tains vast deposits of guano. An island, during an earthquake, rose up in the bay of
Callao, some years since, from the sea, containing guano four feet deep, the formation
the same as the Chincha islands.” In conclusion, he says, ‘‘the day will come when
the guano at these islands will be dredged up with boats like mud from our rivers and
harbors.” And in this expectation I fully coincide with Mr. Nash.

Sea mud has been found to yield an excellent article of fertilizer, and
is collected for that purpose at different points along our coast. That
from the harbor of Charleston, S. C., yielded to the late Prof. Bailey a
rich harvest of diatomaceous forms; and I have examined the same
material, as well as that used in Salem, Mass., for the same purpose,
and known as “mussel bed,” and have found them both to be full of
microscopic forms.

Some years since Prof. Gregory described a remarkable deposit of sand
from Glenshira, which he considered to be fossil, and called it post-ter-
tiary. It was full of the remains of diatomacee, both marine and fresh
water, and had been formed evidently by the ingress of the salt water of
the bay into a fresh water pond. Occasionally we find the bottom of
fresh water marshes upheaved and everted by superincumbent pressure
from railroads or other passage ways being built across them. Under
these circumstances there are often developed deposits of the remains of
diatomaceze. I have one such specimen from Detroit, Mich. I have also
seen two examples of the everting, in this way, of the ancient bed of salt
marshes, and in both cases the remains of diatomacez are plentiful.

The importance of a knowledge of the diatomacez to the geologist
has been lost sight of up to the present time; but now that the state of
New Hampshire has taken the lead in this matter, it is to be hoped that
they will be studied, as they occur in the rocks of other localities.

478 PHYSICAL GEOGRAPHY.

PAR YT “SE Var Nr its

DirEcTIONS FOR COLLECTING, PRESERVING, AND TRANSPORTING
SPECIMENS OF DIATOMACE-®.

The diatomacez constitute a group of organisms of so much interest
to the student of natural history, that it is desirable that specimens
should be collected in various parts of the world. That such collections
may be of value, it is necessary that they should be made in a proper
manner; and for the purpose of facilitating the making of such collections
these directions have been drawn up. The directions given should be
closely followed, as the methods described have been found, after consid-
erable trial, to be those yielding the most satisfactory results. As the
fossil deposits containing the remains of diatomacez are most readily
recognized, gathered, and forwarded, they will be first described.

Fossil Deposits. Included under this head must be considered the
enormous sub-plutonic strata found on the Pacific coast of North Amer-
ica, so that the fossil deposits of diatomaceze may be said to contain both
fresh-water and marine species, though never in a mixed state. In some
cases the particular species present indicate the character of the piece of
water in which the deposit has accumulated, different forms, or groups
of forms, appearing in bays, ponds, lakes, marshes, springs, and rivers, and
at various points of elevation above the surface of the sea.

The principal fossil deposits of diatomaceze hitherto discovered contain
marine species, and extend over considerable tracts of the earth’s surface.
The most important stratum of this character is considered to belong
to the miocene tertiary, and is found on the Atlantic side of North
America, not far from, and, in fact, in some places, reaching down to
the coast. It is known to extend from the Patuxent river, in Maryland,
as far south as the city of Petersburg, in Virginia. How much beyond
these two points it extends has not been ascertained, but is found under-
lying the cities of Petersburg, Richmond, and Fredericksburg, in Virginia,
and at many other points in that state as well as in Maryland. It is
desirable to obtain specimens from different points in this bed, as it varies
in character, and contained organisms with every few miles of surface,
and at different points in its depth.

NATURAL HISTORY OF THE DIATOMACE. 479

Strata of this kind vary greatly in appearance, as well as in micro-
scopic character. Therefore the following general directions will suffice
to guide collectors in searching for and detecting them.

Gather all earths of light color, varying from a pure white, through
different shades of grey, cream, and fawn, to an iron-rust tint. The
texture is often friable, and then looks somewhat like clay, especially
when it is wet; at other times it is of a hard and stony character,
though always more or less porous, and, when soft, of little weight.
A moderate magnifying power shows it to be made up of the shells
of diatomacez. Collect enough to make up three or four pounds’
weight, or, say, a block six or eight inches square, and, if possible, from
the surface and at various depths, for the reasons already stated. Some
of the localities of this material may be mentioned. In Virginia it has
been procured in and near Petersburg and Richmond, at Shockhoe hill
and Church hill, and at Hollis cliff; and in Maryland, at Lower Marlboro’,
Nottingham, Piscataway, and Rappahannock cliff.

Besides the above mentioned, an extremely interesting stratum of a
similar character, but in general of harder texture, has been found on
the Pacific coast of North America, and extending at least from San
Francisco to the lower border of California, if not farther, in both direc-
tions. This substance makes up the major part of the rocks of the coast
range of mountains, and has been named the bituminous shales. It was
first detected at Monterey, and is known to microscopists in England as
“Monterey stone,” but it has since been traced and brought from various
points. Santa Cruz, San Pedro, and San Diego have yielded excellent
specimens containing many beautiful forms of diatomacee. It is usually
light fawn-colored, and distinctly stratified. Large fossil shells are found
in it; and associated with and in, if not derived from it, is the bitumen of
California. At Baldjik, near Varna in Bulgaria, on the Black sea, is a
stratum of stony character, having shells and bones dispersed through it.
The diatomaceze found in it are apparently of brackish-water origin, and
this is the only stratum of this kind that is known. But very little of
this material has found its way into the hands of naturalists. On the
island of Jutland, in Denmark, is found a polishing slate which is rich in
diatomaceous forms not found anywhere else. This, also, is rare among
naturalists, and a good supply of it is very desirable. At Oran in

480 PHYSICAL GEOGRAPHY.

Algeria, Africa, and at AZgina and Caltanisetta in Greece, are deposits
containing the remains of diatomacez intermixed with polycystina and
foraminifera, and referred to the Cretaceous. In the island of Barba-
does are so-called marls made up of diatomacez and polycystina, the
latter in great numbers and very beautiful. In the island of Trinidad, at
South Naparima, a similar stratum has lately been discovered which “is
considered as connected with the new red sandstone; adjoining to which
is the sandstone, probably of the same description, in which the Pitch
lake is situated.” At Moron, in Spain, has been found a similar deposit
of marine diatomacez; and still another was discovered by Dr. C. F.
Winslow at a point about seventy miles south of the town of Payta, in
Peru, and about fifteen miles from the Pacific ocean. Here is a plain
separated from the sea by a range of hills several hundred feet high.
Within the plain is a depression with nearly perpendicular walls two
hundred feet high, the bottom of which depression is at about the level
of the sea—perhaps a little lower. The surface of the soil thereabouts
is covered with salt. For fifteen feet down there is a deposit containing
recent shells, the bones of cetacea, and pebbles; then, for one or two
feet, is a yellow loam, and, at the bottom, is the stratum, containing the
diatomacez, which is from two to four feet thick. The amount Dr,
Winslow brought away was very small, and this is all that has got into
the hands of microscopists. Prof. Pumpelley brought from near Netanai,
in Japan, specimens of a like deposit. Very small fragments of the
strata from Jutland, Trinidad, Moron, Payta, and Japan have been se-
cured; so it is extremely desirable that those localities should be again
visited, the geological relations of the strata ascertained, and a plentiful
supply of the material gathered. The sub-plutonic deposits seem to be
confined to the Pacific coast of the North American continent, and near
by. At Five-mile cafion, near Virginia city, Nevada, is an enormously
thick stratum of this character, which is ground and sold considerably
under the name of “electro silicon,” as a polishing powder. At Klamath
lake, on the banks of the Columbia and Pitt rivers, and elsewhere, at
many points, these deposits have been found.

The rules already given hold good with regard to gathering specimens
of all of these deposits. Everything that can be ascertained with regard
to their position and relations should be noted. Also, any fossils con-

NATURAL HISTORY OF THE DIATOMACE, 481

tained in them, or in the strata above or below them, should be gathered,
and their position noted on the labels accompanying them. All specimens
should be kept carefully separate (not even permitting them to come in
contact) by wrapping each one in paper, placing within a label having
written upon it zz zzk the exact locality, date of collection, and name of
collector. It is also desirable that note should be made of the depth
from the surface at which the specimen was taken, together with any
other information that may be deemed of interest, as supposed extent of
stratum, slope-upwards towards north, south, east, or west, and thickness.

Lacustrine Sedimentary Deposits. These were called by me at one
time sub-peat deposits, from the fact that all I had seen up to that time
had been discovered beneath peat; but as the number of these strata
which have come into my hands has increased, I have seen many which
do not occur under such circumstances; hence the above name has
been applied to them as being more appropriate, and indicating their
most common mode of occurrence. In England they are called fossil;
but in the true acceptation of that term the forms contained in them
are not fossils, but are identical with living species.

They are generally of a pulverulent character, and, when dry, are of
little weight, so much so as to attract attention. When free from organic
matter, as occasionally occurs, they are quite white, looking almost like
powdered starch; but most commonly they are grey, which looks dark
while the material is wet, but when dried the color is light. A mass of
about six or eight pounds’ weight should be secured, and the same pre-
cautions as to keeping separate and labelling specimens adhered to, as
have been already mentioned. As these beds are seldom of any great
extent (they often soon become obliterated or covered up), it will be well
to secure a good supply of the material while it is accessible. If any
shell, wood, or other organic remains should be found dispersed through
the deposit, or overlying or beneath it, they should also be secured, and
their position recorded on the label. Likewise, a sample of any superin-
cumbent peat should be kept for future examination. In Sweden and
Norway, and in Lapland, these deposits have been used to eke out a
scanty supply of flour during bad seasons; but they can hardly be said
to be food, for they are not nutritious, but most likely only act by their

mass distending the stomach, and thus allaying for a time the pangs of
Voir i 6S

482 PHYSICAL GEOGRAPHY.

hunger. They have likewise very frequently been employed, under the
name of “tripoli,” as a polishing material, and are excellent for that pur-
pose. In some parts of this country they go by the name of “marl,” but
they are not examples of that substance, which is calcareous, being made
up of the remains of the shells of mollusca. Specimens from every
locality are desirable.

Muds and Deposits from the bottoms of harbors, bays, lakes, ponds,
estuaries, and rivers. As a general thing these are not of very great
value to the microscopist for the remains they contain, and it is only de-
sirable to collect them in localities or under circumstances where other
gathering cannot be made, or when they are known to contain any organ-
isms of great beauty or rarity. The blacker and softer the mud the
better, for, if it contains much sand or gravel, the minute organisms will
be present in just so much less proportion. As much as can be conven-
iently transported, say about a handful, should be collected, and, if possi-
ble, not dried, but placed in a bottle and tightly corked; or, it may have a
little glycerine added to it, which will prevent its drying,—for it has been
found that muds, and especially those from salt-water, when once dried,
are only with difficulty broken down again so as to be cleaned. The
mud and slime attached to anchors, buoys, and submerged woodwork,
together with the scrapings from the bottoms of vessels containing shells,
plants, zoophytes, etc., may be simply dried in the sun, and then havea
label attached. The mud from beneath fresh water is of little value, as
it rarely contains any organisms of beauty; but the marine forms found
in mud are occasionally fine, beautiful, and rare.

Guano. This substance often contains species of diatomacez not
otherwise obtainable. It is the ammoniacal guanos alone, however, which
I have found to yield any great number of diatomaceous forms; but
there are certain guanos, of which one known as “Bolivian guano” is an
example, partly ammoniacal and partly phosphatic, which contain some
forms not otherwise obtainable. Quantities of a pound or two in weight
should be secured, and the exact locality of the island or other place from
which it was obtained, together with the latitude and longitude, and other
information that may be collected and deemed of interest, should be
marked zz zzk upon the label.

Shell Cleanings. The sand, mud, algze, zodphytes, and similar matters

NATURAL HISTORY OF THE DIATOMAECE, 483

adherent to marine shells, which are commonly removed by students of
conchology, have often been found to yield rich harvests of rare forms of
diatomaceze. Such material can be washed, or, still better, scraped off of
the living or dead shells (the dirtier such shells seem the better, of course),
placed in paper and plainly labelled with the exact. locality, and, if possi-
ble, name of the shell and depth of water from which it was taken. Con-
chologists will do well to save all their shell-cleanings for this purpose.

Marine Invertebrata. Specimens of the entire animal, or the contents
of the stomachs of echinoidea (sea urchins) and holothuroidea (sea cu-
cumbers), should be secured, as it has been found that many, if not most
of them, are vegetable feeders, and thus take into their stomachs algze
which have diatomaceze growing upon them. The entire animal should
be preserved in spirits (if alcohol is not procurable, brandy or whiskey
will answer), but if that be not convenient, they, as well as the contents
of the stomachs, may be dried without washing in any way. It has been
found that holothurians, when they are immersed in spirit, often turn
their stomachs inside out, and thus the contents, which are the part most
valuable for the microscopic organisms, will be found at the bottom of
the containing vessel. When the whole animal is preserved in spirit, the
label may be written in ink on stiff paper or parchment, and, when quite
dry, tied to the specimen and immersed with it in the spirit. In this way
several specimens can be preserved in the same vessel, and space econo-
mized. This method will be found to be the best, as labels pasted or
gummed on, or otherwise attached to the vessel, are liable to be obliter-
ated from leakage of the contained fluid, or removed during transporta-
tion. The stomachs of mollusca (shell fish) and crustaceans (lobsters,
crabs) also occasionally yield specimens of diatomacez, and it will be
well to secure specimens of those creatures in the manner described.
The stomachs of fish occasionally contain diatomacex, and may be
secured.

Soundings. The material brought up from the ocean bed by the
sounding-line, or the larger masses procured by means of the dredge,
have been found to yield good returns of microscopic treasures when
examined. The calcareous shells of foraminifera, as well as siliceous
polycystina and diatomacee, are found in them. When kept for this
purpose, note should be made of the latitude and longitude, depth of

484 PHYSICAL GEOGRAPHY.

water, along with the name of the vessel and collector, and the date of
collection.

Lhe dust which collects at sea upon the sails or decks of vessels. This
kind of material, although not common, has been found to be of interest
when examined microscopically. It can generally be scraped up with a
piece of paper. When the quantity is so small that it cannot be col-
lected in this way, a piece of damp paper may be laid on it once or
twice, in several places, and then folded up before it becomes dry. Lati-
tude and longitude, direction of wind at the time of the falling of the
dust, name of vessel, date, and collector’s name, should be noted on the
label.

Recent gatherings of Diatomacee. These are the most valuable, im-
portant, and rich of the gatherings containing diatomacez on which the
student depends for material for investigation, and they are so various in
character that it becomes difficult to give general directions that will
serve to indicate the modes of procedure to be followed in securing
them. To collect diatomacez at all thoroughly, a considerable amount
of knowledge of their habits is necessary. In general, it may be said
that gatherings should be made of marine plants, or algz as they are
called, which grow entirely submerged beneath the water, attached to
rocks, piers, iron-, or wood-work. The dirtier such plants appear to the
naked eye, the richer will be the harvest of minute organisms secured,
as the brown coating, seen upon aquatic plants and similar submerged
objects, obscuring them, is but a mass of living diatomacese. The larger
and coarser algee,—more especially those having a slimy feel—do not
usually yield many diatomacez; but the finer brown, red, or green fila-
mentous kinds are commonly covered with them. Detached fragments
thrown up upon the beach ought not to be kept if living ones can be
found, for they usually have had the diatoms rubbed off from them, and
are, besides, contaminated with sand. The living algze taken from their
attachment should be dried without washing or much compressing, and
may then be placed in layers, each specimen being plainly labelled with
the exact locality, date of collection, and collector’s name. Fragments of
algae, which may break off from cabinet specimens, and would be rejected
by students of the algae, may yet be of value to the diatomist. Some of
the finest collections I have ever seen were derived from this source.

NATURAL HISTORY OF THE DIATOMACE, 485

When known, the name of the alga should be stated. If possible, it
is extremely desirable to secure specimens of diatom-encrusted algz in
spirits. In this way the diatoms will be preserved in almost their natu-
ral condition; and those species, which are filamentous or grow in chains,
will be available in that condition for study.

Fresh-water plants clouded with diatomaceze may be collected and
preserved in the same manner as marine alge. As has been remarked,
the finer filamentous species of water plants yield the best results; the
marine fucoids, as the “bladder wrack,” and similar species, secrete a
mucus which seems to be repugnant to the growth of most diatoms; yet
upon the stalks of Laminaria, and some other large olive-colored alge, are
found the finer red-tinted species, which are themselves beautiful objects
of study, and are, in turn, the homes of hosts of minute forms of life.
Water plants, marine or fresh-water, should not be cleaned in any way,
but merely raised from the water, and, after draining for a short time, be
either laid upon a piece of clean paper to dry, or hung up where the air
and sun can rapidly evaporate the moisture. Marine plants will usually
not dry thoroughly, as the salts present in the water absorb moisture
from the air; hence they are liable to mould unless they are packed in
paper. The moss-like carpeting seen upon submerged rocks is often
made up of beautiful specimens of the filamentous species of diatoms
alone, and it will be well to scrape the surface of the stone, and, placing
the mass in a bottle, cover it with alcohol, which will become colored
from dissolving the coloring matter of the diatoms, and preserve them
in the very best manner for future study. Fresh-water forms are very
often found hanging in green-colored festoons from the exit pipe of
drains, sluices, or fountains, and may be preserved in the same way.

The green, brown, or fawn-colored scum which floats upon the surface
of the water of road-side pools, ponds, bogs, marshes, or rivers, consists
usually of little else but diatoms, and may be taken up by means of a
spoon or bottle, and then preserved in alcohol or dried upon paper. The
surface of the sea may be skimmed by means of a net of fine muslin,
having an opening left in the bottom, in which a four- or six-ounce wide-
mouth phial is tied, and towed at the stern of avessel. If the sea-water
be strained through such a net, either by towing behind a boat or even
poured from a pail, the solid matter contained in it will be washed down

486 PHYSICAL GEOGRAPHY.

and gradually collect in the phial, which can then be removed and tightly
corked, and another substituted. Some very beautiful forms have been
procured in this way. The stain occasionally seen on the surface of the
sea in some latitudes, as well as the minute organisms causing the lumi-
nosity of the ocean, yield rich crops of diatoms, and should be secured.
Such gatherings may be put up as obtained, or have alcohol added to
them for better preservation. The collection of aquatic plants from the
mouths of rivers is extremely desirable—such as have been made in the
delta of the Ganges yielding interesting results. The refuse of dredging
for shells often yields mud, old shells, or algae; and collectors will do well
to secure such.’ Experience, however, will teach the best places to look
for recent diatoms; but the above general directions will prove of service
to those who are new to the pursuit, or who collect for others.

It should always be remembered that a knowledge of the exact locality
is of the greatest importance,—so that upon the label should be written
in ink the locality, date of collection, and name of collector. Other
facts deemed of interest may also be added.

PARE. BIGHT HH.

How To Prepare Specimens or DiATtoMAcEa& FOR EXAMINATION AND
Stupy By MEANs or THE Microscope.

Having accumulated a number of gatherings of rough material, which,
a cursory examination has shown, contain specimens of diatomacez, and
which, it is judged, it will answer to clean and otherwise arrange and put
up, or, as it is technically termed, “mount,” for future study, the intend-
ing diatomist requires to be informed how he may best set about pre-
paring his specimens in the most advantageous manner. The author of
the present sketch has published, in the seventh volume of the Procced-
angs of the Boston (Mass.) Society of Natural History, certain directions
for collecting, preparing, and mounting diatomacez for the microscope;
and, as that paper contains a large part of the information he desires to
impart at the present time, he will draw upon it pretty freely, supple-
menting it to such a degree as later investigations warrant, or as may
seem desirable.

Although most of the published treatises on the use of the microscope
in general profess to give directions for mounting objects in such a

NATURAL HISTORY OF THE DIATOMACEE. 487

manner as to preserve them for almost any length of time, and at the
same time exhibit their characters to the best advantage, and although
we have in the English language at least three books treating specially
of this subject of the preparation of microscopic objects, yet hardly any
one of these volumes gives any concise, practical, and, at the same time,
reliable descriptions of the best methods of collecting, preparing, and
mounting specimens of diatomacea. In books, generally, when the
preparation of these organisms is treated of, it is usually the fossil
deposits which are considered, and even such directions as relate to
these are for the most part meagre and unsatisfactory; and, when the
specific and special directions are, as is often the case, copied from one
book into the other without having been tested by the copyist, any
faults they may have possessed, as originally written, are merely repeated
and not eliminated. To prepare and mount specimens of diatomacez,
for the purpose of sale alone, is one thing, and to prepare and mount
them, so as to preserve and exhibit their natural characters and fit them
as objects of scientific study, is another and very different thing. The
latter can only be attained after considerable practice, and to do it prop-
erly a considerable amount of knowledge of their natural history is
plainly necessary.

The diatomacez should always be prepared and put up for a special
purpose,—that of exhibiting characters peculiar to genera and species;
and to do this those characters must of course be known. Muds,
guanos, dredgings, and gatherings of that description can seldom be
used for the purpose of exhibiting such characters, and when they can,
in exceptional cases, be so employed, it is when the forms they contain
are selected out in the manner to be described hereafter. Gatherings,
likewise, which contain many species in a mixed condition, should, as a
general thing, be rejected unless there be present something of special
importance, such as rare species, or some large and fine or distorted
forms of common species. But even in such cases it will be found best
not to mount the gatherings as collected, but to select out the forms
desired and place them upon slides by themselves, and in such media as
will exhibit their peculiarities to the best advantage. Of course it may
be desirable to study the geographical distribution of the diatomacez ;
and then mixed gatherings become of value as exhibiting the number of

488 PHYSICAL GEOGRAPHY.

forms occurring at a particular station. Then, again, the fossil as well
as the semi-fossil deposits and guanos may be cleaned and mounted as
obtained; but even then it may become desirable, if space can be spared
in the cabinet, to have the various species found in each gathering sepa-
rately mounted, so that they may be at any time studied in comparison
with similar forms from other localities.

General directions for collecting diatomacee have been already given
in Part Seventh; but it will be desirable to again allude to a few points
in connection with this portion of our subject. Some years since, an
article entitled “Hunting for Diatoms” was published in a London
journal called Zhe Jutellectual Observer. The author’s name was not
given, but internal evidence would seem to indicate that it was penned
by a deceased botanist of note, who was a decided authority on this
branch of biology. This paper contains some valuable hints respecting
the places in which to look for diatoms, and some of the suggestions
contained therein I have ventured to transfer to these pages, as they will
be found of value to the intending diatomist. Thus, the exquisite Arach-
notdiscus, Triceratium Wilkesti, and Aulacodiscus Oregonensis, may be
looked for on logs of wood which have been floating in the sea, and
imported from New Zealand, or Vancouver’s island. So, on logs from
Mexico and Honduras may be found the curious Zerpsin@ musica. The
nets of fishermen, especially from deep water, may yield alge bearing
such forms as Rhabdonema arcuatum or Adriatium, Grammatophora
serpentina and marina, various Synedras, and other fine forms. On
oyster shells may be found alge bearing upon their fronds Liddulphia
regina, Batleytt or aurita. Rhizosolenia styliformis is said to be almost
sure to be there likewise. After a ship is unloaded, and as it floats
higher in the water, its sides may be searched for treasures of the diatom
world, and Achnanthes longipes and brevipes found, or even Diatoma
hyalinum and Hyalosira delicatula. The sea-grass, or Zostera marina,
growing along our coast, often bears upon its waving ribbons fine forms
of diatoms, and that used for stuffing chairs, and lounges or mattresses,
and imported from abroad, will yield foreign species to the collector.
There is a plant known in England as “Dutch rushes,” which is imported
into that country from Holland, and which is used for chair bottoms.
These plants grow in the brackish water of the marshes, and hence upon

NATURAL HISTORY OF THE DIATOMACEE, 489

them are to be found the delicate Coscinodiscus subtilis, Eupodiscus
argus, and Triceratium favus. Both of these two last named forms occur
commonly on our Atlantic coast, and muds from Charleston, S. C., and
Wilmington, Ga., have provided me with them in plenty. Cargoes of
bones, which present green incrustations from having lain in the water
for some time, are said to yield diatoms, some of which may be rare, as
coming from foreign ports. The state of New Hampshire has not yet
been sufficiently gone over for it to be said what the characteristic forms
of diatomaceze growing within its boundaries are, but yet we may safely
predict that the lakes, ponds, streams, and sea-coast of that state will
yield to the searcher ample material of beautiful forms.

If the microscopist wishes to mount a few slides of recent diatoms
just to show what diatoms are, nothing is easier. It is only necessary to
boil a small mass of them in strong nitric acid in a test tube over a spirit
lamp, and, when the acid has ceased to emit red or yellowish fumes,
wash them thoroughly with clean water, allowing them to settle com-
pletely. Then a little of the clean sediment, consisting almost entirely
of the shells of the diatoms, is taken up by means of a “dip-tube,” and
placed upon the central portion of a glass slide. Here it is dried, and the
slide warmed over a lamp; then a drop of Canada balsam is permitted to
fall upon the diatoms. As soon as all bubbles have cleared off from the
balsam, a warm cover of thin glass is carefully laid upon it and permitted
to settle into place. When cool, it is ready for examination by means of
the microscope, any balsam which has exuded around the cover being
washed off with alcohol. In this way rough and tolerably clean speci-
mens may be obtained; but such would not, or, at all events, should not,
satisfy the student of the diatomacea. For him more elaborate methods
are necessary, and these we will now proceed to consider.

Apparatus and chemicals necessary. A chemist’s retort-stand, which
is a heavy iron plate with an upright rod projecting from one side of it.
Running on this rod, and so arranged that they may be fixed by set-
screws at any height, are a series of rings of various diameters, which
are to be used to hold the vessels in which the specimens are to be
manipulated over the source of heat used. Mr. C. G. Bush, late of Bos-
ton, Mass., who has had considerable experience in cleaning diatomacee,

tells me that he uses a lamp burning petroleum oil, as cheaper than a
VOL. I. 64

490 PHYSICAL GEOGRAPHY.

spirit-lamp, and, to support the vessels he employs, has a little metal
arrangement on the top of the chimney, such as is supplied for the pur-
pose of holding a small tea-kettle and the like. The only objection to
the oil-lamp is, that, unless the wick be well turned down, we are liable to
have our vessels blackened. However, the heat given off by burning
petroleum is very great, and I have often used such a lamp with advan-
tage. If desired, of course, the source of heat used may be gas, burned
in a Bunsen’s burner, or a spirit-lamp; and this last, especially if it be
supplied with a metal chimney to cut off draughts, is, all things consid-
ered, the best, as it is very cleanly, not being liable to smoke the bottom
of the glass or porcelain vessels used. If we are going to work with
large quantities of material, we shall require a small sand-bath to heat
the glass vessels upon. In small quantities, the diatoms may be boiled in
test-tubes, when some sort of holder will be required. The metal ones,
sold by dealers in chemists’ apparatus, are extremely handy; but I have
found that we can make very good ones out of old paper collars. One of
the kind called “cloth-lined” may be cut into strips about three quarters
of an inch wide and three inches long. Such a strip is folded around
the test tube, near the top, and the ends, brought together, are held
between the fore-finger and thumb. In this way the tube is firmly
grasped, and can be held over the lamp without much danger of burning
the hand, as the paper collar strip is a bad ‘conductor of heat; or, the
paper strip may be grasped in an “American clothes-peg,” which has a
spring to force its parts together. Large quantities of diatoms are best
boiled in porcelain evaporating-dishes, glass flasks, or beaker-glasses.
The last mentioned vessels are also by far the best things for washing
them in. A few, say three or four, glass stirring-rods will be found
useful; and one or two American clothes-pegs to take hold of hot evap-
orating-dishes with. Then there will be required a few dip-tubes, made
of small glass tube, drawn out over a flame, so that the opening is con-
siderably diminished. The mode of making these cannot be given here,
but will be found in books on chemical manipulation; and it will be well
for the student to learn to make his own dip-tubes, as a number will be
required first and last, and they are easily broken. Of course there will
be required a number of glass slides, of the usual dimensions of three
inches by one. These should be of as white glass as possible, and it will

NATURAL. HISTORY OF THE DIATOMACEZE. 491

be found best to procure those with ground edges, as they are the neatest
in appearance. Only such as are free from scratches or other blemishes
in the central square inch should be used; and, although even such as
have bubbles or scratches near the ends only will not look ornamental in
a cabinet, we should remember that microscopic objects are not generally
mounted to look well in a cabinet, but to be useful out of it; so that if
the central and useful portion of the slide be perfect it need not be
rejected. Some persons make their own glass slides, but I have never
found it answer to do so, as it is difficult to get the right kind of glass,
not at all easy to cut it or grind the edges, and it is liable to be scratched
while cutting or grinding. Thin glass, such as is made on purpose for
microscopic use, will be required; and this, also, it will be found best to
buy ready cut rather than attempt to cut it for one’s self. The thin glass
used for covers may be of different thicknesses, but the thickest made
will not do for diatoms, and a certain amount of the very thinnest will be
required for small and delicately marked forms, on which very high power
objectives will have to be used. The covers must be perfectly clean,
which may be insured by soaking in caustic potassa solution, and then
washing thoroughly in clean water. The thinner kinds of glass are rather
difficult to clean; but with a little extra caution it may be accomplished,
the last polish being given to it by a piece of an old and well-worn cam-
bric handkerchief. The covers, always round, should be separated into
sizes and thicknesses, so that the exact kind of cover required can be
found without having to search for it by turning over a number, scratch-
ing or breaking them, and losing much valuable time. We shall also
require a pair of forceps for holding the slides over the lamp; and such
as are sold at house-furnishing stores and by grocers, under the name of
American clothes-pegs, and which have been already mentioned, are by
far the best I have ever seen or heard of. A small pair of brass forceps
which close with a spring will be needed, and they are best set in a
wooden handle so as to protect the fingers from the heat; and another
pair, which spring open and may be closed by means of the finger and
thumb, will be wanted for taking hold of and adjusting the thin covers.
I do not advocate the use of paper covers for slides, but labels of some
kind will, of course, be required, and I have found the plain circular white
ones to look the best. There are very pretty square labels sold by dealers

492 PHYSICAL GEOGRAPHY.

in these things that I have used and liked. For making cells to hold
specimens put up in fluid, a turn-table and brushes and some cement will
be necessary. The cement I use and prefer above all others is good old
gold size, used warm. .

The chemicals required are nitric acid, sulphuric acid, hydrochloric
acid, bichromate of potash, caustic potash, alcohol, and, above all, a plen-
tiful supply of clean, f/tered water. The water should be such as leaves
hardly any residuum when a quart of it is evaporated to dryness; and it
must be filtered just before use, to remove any minute organisms, dia-
toms especially, which it may contain. A certain amount of washing
soda will be wanted, if guanos are to be cleaned.

We will now proceed to consider the manipulations necessary to pre-
pare the various kinds of gatherings, always remembering that these
methods will have to be modified to a certain extent for each specimen.

Recent Gatherings. If there be sand in the gathering, it will be well
to remove it before using acid by shaking it in clean water and pouring
off before the diatoms, which are lighter than the sand, settle. The
water holding the diatoms in suspension may be poured into a test-tube
or beaker, the diatoms allowed to settle, and as much of the water
poured off as possible. The diatoms are now covered with nitric acid to
about the height of half an inch, and allowed to stand for a few minutes.
Usually, some chemical action takes place, and it will be well to wait
until it subsides. The test-tube or beaker is then held over the lamp
and carefully heated until the reaction of the acid upon the organic mat-
ter of the diatoms ceases. Thereafter, and while the liquid is still hot, I
have found it often advantageous to drop in one or two fragments of
bichromate of potash. The organic matter is more thoroughly destroyed
in this way than when the acid is used alone. Thereafter it is well to
pour the acid and diatoms into a capacious beaker of clean water, wash-
ing the tube or smaller beaker out with a little water, and adding this to
the other. After the diatoms have all settled, which will often require
hours, the supernatant fluid is carefully poured off, and a fresh supply
added; and this must be repeated several times until all of the acid and
colored chromium compound has been removed. When this point is
arrived at can only be ascertained from experience. In this way the
valves and connecting membranes of the diatoms are usually separated

NATURAL HISTORY OF THE DIATOMACE, 493

and cleaned ready for mounting, which process will be described here-
after.

Muds will have to be treated in a somewhat different manner from
recent gatherings. If the mud is dry, it will have to be broken down by
boiling for a few minutes in a solution of caustic potassa, the strength of
which must be apportioned to the particular specimen under treatment.
After it has been broken down into a soft mud, all of the potash is thor-
oughly washed off by means of clean water, and replaced by nitric acid,
as in the case of recent gatherings. This is boiled, and a little bichromate
of potash added as before, and the whole washed. It very seldom hap-
pens that the diatoms occurring in mud will be sufficiently cleaned by
this process, so that it has to be supplemented by another. The sedi-
ment is therefore washed into one of the evaporating-dishes and allowed
to settle, and as much of the water poured off as possible. Then sul-
phuric acid, in quantity to a little more than cover them, is poured in,
and the vessel gradually and carefully heated. As soon as the liquid
shows signs of boiling, bichromate of potash is added, a very little at a
time, until the green color first formed by its reaction upon the organic
matter begins to assume a yellowish tint, when no more is dropped in;
but a few drops of hydrochloric acid are permitted to fall in, and the
liquid is allowed to cool. Of course it will be best if the person under-
taking to clean diatoms is somewhat versed in the use of chemicals; but
at any rate care must be taken not to drop any of the acids upon the
clothes or skin, and great caution must be exercised in not inhaling any
of the vapors given off. Those evolved after the addition of the hydro-
chloric acid are especially irritating and dangerous, and must be avoided.
As soon as the liquid has cooled a little, water should be added cau-
tiously, as great heat will be generated thereby, and there will be danger
of its boiling over. Thereafter it may be poured into a large beaker-
glass of water and thoroughly washed, as in the former case. If it be
found that the precipitate is not quite white, it will be necessary to boil
it again in sulphuric acid, with bichromate of potash and hydrochloric
acid, until it is quite clean. If, on examination by means of the micro-
scope, it is found that there is much flocculent matter present besides
the diatoms and sand, this can be removed by boiling for a few seconds
in a weak solution of caustic potash, and washing quickly and thoroughly

494 PHYSICAL GEOGRAPHY.

with plenty of clean water. When we have recent gatherings of fila-
mentous or stipitate forms of diatomacez, which we desire to preserve in
the natural condition, they should be immersed for about twenty-four
hours in alcohol to dissolve out the endochrome. If this does not
answer, it will be well to soak the mass of diatoms or plants upon which
they are adherent in a solution of hypochlorite of soda, an impure variety
of which is sold in the shops under the name of Labarraque’s disin-
fectant, for about the same length of time. This will generally destroy
all color, and leave the specimens transparent. It is best, however, in
many cases not to remove the endochrome, but leave it, and mount the
specimens in such a way as to show them in as natural a condition as
possible. How this may be done will be described hereafter.

Guanos. The preparation of these substances so as to obtain the
microscopic organisms they may contain is rather difficult, tedious, and
dirty, and should only be undertaken by a person somewhat versed in
chemical manipulations, and in a proper room as a laboratory, where
there is no danger of harm resulting from the fumes evolved. As the
ammoniacal guanos are those which contain the most diatoms, and con-
sequently which answer best to clean, we will begin with them, and take
as a type that which comes from the islands on the coast of Peru. As it
comes into commerce this guano is a moist powder of a light iron-rust
color, smelling strongly of ammonia, and having scattered throughout its
mass lumps of ammoniacal salts of a more or less solid consistency.
The guano should be thinly spread out upon a stiff piece of paper and
exposed to the air, and, preferably, to a moderate heat for several days or
even weeks. In this way most of the moisture and much of the ammo-
nia will evaporate, and less acid will be required to clean the guano. It
will now have become much lighter in color, and crumble to a dry powder.
A tin pan is now about half filled with a solution of common washing
soda in clean filtered water, and placed over some source of heat, as on
a stove. The strength of this solution is not a matter of any great
moment, and must vary with the guano manipulated. As soon as it
begins to boil, the guano is dropped gradually in, a little at a time, while
the liquid is stirred with a glass rod or stick of wood. Considerable
effervescence takes place, ammonia being given off, and therefore it must
be kept continually stirred, and care exercised to prevent its boiling over.

NATURAL HISTORY OF THE DIATOMACEE, 495

After a while it is poured into a plentiful supply of clean water and
washed therewith several times, care being taken to permit all of the
diatoms to settle. As soon as the wash-water is only slightly colored,
the guano is transferred to a good sized evaporating-dish, and covered
with nitric acid, and boiled. While it is boiling, a few crystals of bichro-
mate of potash are dropped in, and the material washed as in the case
of muds. Thereafter the diatoms are boiled in sulphuric acid with
bichromate of potash and hydrochloric acid, as before described.

Phosphatic guanos, as that from Brazil, are somewhat more difficult to
treat. They are generally drier than the ammoniacal kind, and must be
boiled in a large quantity of hydrochloric acid as many as three times,
and the acid must be poured off while still hot. Thereafter nitric acid
and sulphuric acid and bichromate of potash must be employed, as in
the other case.

Lacustrine Sedimentary Deposits. For the most part these are pul-
verulent, and easy to clean. Some, as found in nature, are so pure that
they require no cleaning except washing in clean water. Burning on
a plate of platinum or mica will often serve to clean some specimens,
but it will, in general, be found best to boil in nitric acid with a little
bichromate of potash, and subsequently in sulphuric acid and bichromate
of potash, with the after addition of hydrochloric acid. Occasionally a
certain amount of flocculent matter will be left, which it will be necessary
to remove with very careful heating, not boiling, in a weak solution of
caustic potash, and immediately pouring into a large quantity of clean
water and thoroughly washing.

Marine Fossil and Sub-Plutonic Deposits, being stony and possessed
of very much the same physical characters, are manipulated in the same
manner. A small lump of the deposit is placed in a test-tube, and cov-
ered with a strong solution of caustic potash. It is then boiled for a few
minutes, and usually it immediately begins to break up and fall down in
the shape of a soft mud-like material. At once the liquid, with the sus-
pended fine powder, is poured off into a large quantity of clean hot water,
and if the whole of the lump has not broken down into a powder, what
remains has a little water poured over it in the test-tube, and it is again
boiled. It will be found that a little more will now crumble off. This is
added to the rest in the large vessel, and if the lump has not now broken

496 PHYSICAL GEOGRAPHY.

down, it is again boiled in the alkaline solution and in water alternately,
until it has all been disintegrated. It is then all permitted to settle for
at least three hours, when it is thoroughly washed and boiled in hydro-
chloric acid for about half an hour. There is then added an equal
amount of nitric acid, and the boiling continued for a short time. It is
then washed and heated in sulphuric acid, with the addition of bichro-
mate of potash and hydrochloric acid.

All mixed gatherings of diatomaceze, and particularly all muds and
deposits, should be separated into densities, so that for the most part the
larger forms are collected together, free from sand, and separate from
the smaller species and broken specimens. This is done by using a
number of beaker glasses, of various sizes, in the following manner:
Into a one-ounce beaker the cleaned diatoms are placed, and the vessel
filled with water. It is then well stirred up by means of a glass rod, and,
after resting about five seconds, poured off carefully into a six-ounce vessel
so as not to disturb the sand which has settled. Again the vessel is filled
up with water, stirred, allowed to settle for the same length of time, and
poured into the same vessel. This is repeated until it has been done at
least six times, when we shall find all of the sand, free from diatoms, in the
small beaker. This can be thrown away, and as soon as the material in
the large beaker has settled it is returned to the small one, and the same
process gone through with, only extending the time of settling now to
about ten seconds. The next density is that which settles in twenty
seconds; and so on, five or six densities may be obtained, and if carefully
prepared they will be found to contain forms varying very much one from
the other. The large species of 7riceratium, Aulacodiscus, and the like,
will be found in the coarsest density, and the broken diatoms in the
lightest.

Preserving and mounting specimens so as to have them in a condition
Jor study at any future time. Of course, when possible, diatomacez
should be studied in the living condition. But there are many forms
which have not been as yet found living, and these can only be studied
as dead skeletons; and, in fact, it is in the dead skeletons of the diato-
maceze that many of the most marked characteristics are to be found ;
and on such characteristics species have been founded. Besides, the
most beautiful sculpturing of the valves is only to be seen after every-

NATURAL HISTORY OF THE DIATOMACE-E, 497

thing has been removed but the siliceous cell-wall I have termed the
skeleton. Therefore I advocate the cleaning of a portion at least of
every gathering in the manner described, so that nothing will be left but
the clean siliceous cell-wall.

If we desire to keep specimens in a state as near that they present
when living as possible, we have to put them up in some preservative
fluid in which they will not decay, and in which the softer parts will be
preserved. Unfortunately these soft parts do not keep well; but the
fluid which I have found to be the best for the purpose is distilled water,
which has to every fluid ounce two or three drops of wood creosote
added, and thereafter a sufficient number of drops of alcohol, which will
be about double the number of the drops of creosote, to make the creo-
sote soluble in the water, which it is only to a very slight degree under
ordinary conditions. I do not advocate any fluid containing glycerine,
or, in fact, any of the preservative fluids described in the books treating
of the preparation of microscopic objects. The vessel in which the
fresh specimens of diatomacez are put up are what are known to micros-
copists as “cells,” but how these are made cannot be gone into here,
as the description would occupy too much space and time. Suffice it
to say that I prefer cells made of old japan gold-size, which can be
procured of dealers in microscopic materials. Within such a cell, of
sufficient depth and immersed in the preservative fluid, a few of the
diatoms, or a scrap of the plant upon which they are growing, is placed,
and the glass cover fixed over it in the manner described in the books
upon manipulation. The filamentous forms are thus preserved almost in
their natural condition; but, on account of the presence of the endo-
chrome, the sculpturing of the siliceous cell-wall is almost invisible. To
show this character, while the filamentous form is preserved, another
method of mounting is employed. A thin, clean covering glass is
selected, and laid upon a clean piece of paper. A large drop of distilled
water is then allowed to fall upon it, and in this drop the filamentous
diatom is thinly spread out. Then the cover is taken up by means of a
pair of forceps and held over the flame of a spirit-lamp, which has been
turned down so as to be quite small and steady. The cover is held
some distance above the flame, and judiciously manipulated, so that the

heat is evenly distributed over it, and it does not crack. As soon as all
VoL, f ~ 6§

498 PHYSICAL GEOGRAPHY.

the water has been driven off without the formation of bubbles, the
glass is brought gradually down almost in contact with the flame, and
held at that point for a few minutes. -Then the diatoms will be seen to
turn black, on account of the charring of the organic matter contained in
them. After a while this black carbonaceous matter will burn off, and
they will become quite white. If, however, there seems to be any diffi-
culty in burning off the last portions of carbon, the cover is lowered
once or twice to come in contact with the top of the flame, and then
raised again. In this way it will become red hot for a moment; and
everything will be burned off except the siliceous portions of the dia-
toms. Now the cover is removed slowly from over the flame, and held
in the forceps until it is cold, but by no means laid down upon any sur-
face until it is quite cold,—otherwise it will fly into pieces. Then it can
be laid upon an ordinary glass slide, and examined to see if it is worth
preserving, which may be done in one or two ways: first, the glass
cover is warmed, and a drop of good spirits of turpentine let fall upon
it, covering the diatoms. Just before the spirits evaporate, a small drop
of thin Canada balsam is added, and a slide taken, warmed, and a drop
of balsam placed upon the centre part of it. Then the cover is brought
down upon the slide, the two balsam-covered sides together, in such a
way, by tilting the cover slightly, that no air is allowed to come be-
tween them, and the cover permitted to fall gradually into place, driv-
ing a wave of balsam before it. In this way we have the filamentous
diatoms arranged as they grow, but with endochrome removed which
would obscure the markings, and in balsam, which renders them trans-
parent. Some forms, as some of the /vagz//ari@, become too transparent
if put up in this way, and therefore another method of mounting must
be adopted with them. They are burned upon the cover, as just de-
scribed, but mounted dry in air; that is to say, a cell of gold-size is
made, the glass cover slightly warmed, and then placed upon the cell,
with the side upon which the diatoms are fixed, downwards. The
warmth slightly softens the gold-size, and the cover becomes fixed.
Other forms besides the filamentous species may be mounted in fluid,
or burned upon the cover and subsequently put up in balsam, or dry.
But the commonest way of treating such forms is to clean them by means
of chemicals, as already described, and then previous to mounting them

NATURAL HISTORY OF THE DIATOMACEE. 499

divide the clean gathering, consisting of a white sediment of large and
small diatoms along with fine sand, all mixed up together into densi-
ties. Of course, if some of this‘sediment were to be mounted in this
condition, extremely unsightly slides would be procured; so it is best to
separate the finer from the coarser diatoms, and these in turn from the
sand. “This is accomplished by what is known as elutriation, or, separat-
ing into densities after the manner already described. Then slides may
be mounted from each of the densities in the following manner. A slide
is thoroughly cleaned, and a good sized drop of water placed upon the
centre portion. A little of the diatom sediment is then taken up ina
dip-tube, and the point of the tube brought just into contact with the
drop. As soon as a few diatoms have run out of the dip-tube, it is
removed. Then a small splinter of wood or stiff bristle is used to dis-
seminate the diatoms through the drop of water in such a way that they
will be pretty evenly distributed and not overlie each other. The water
is then driven off by heat, a drop of thin Canada balsam placed upon the
dry diatoms, and a cover placed on them in the usual manner. In many
cases, especially when dealing with the smaller forms, it will be found
desirable to mount them upon the cover in this same way, instead of upon
the slide, as they will then be brought as near as possible to the objective
of the microscope. Single or remarkable specimens of diatoms may be
picked out and mounted by themselves ; but the manner of accomplishing
this would occupy more space than it has been thought desirable to
devote to this portion of our subject, and the reader is referred to
the books on mounting microscopic objects for the particulars of the
process.

The main principles of preparing and mounting diatomacece for preser-
vation and study have been given, and the intending student will be able
to devise modifications and improvements for himself, so that he will be
able to put up specimens in as finished a manner-as any to be procured
from the dealers.

500 PHYSICAL GEOGRAPHY.

DESCRIPTION OF PLATES.

All of the figures, with the exception of 23 and 24, are magnified five hundred
diameters, or two hundred and fifty thousand times superficial. Fig. 23 is magnified
about three hundred diameters, and Fig. 24 one hundred diameters. All of the
figures, with the exception of the two mentioned, are exact portraits of specimens in
the collection of the author, and are intended to be as perfect delineations of the
diatoms represented as could be obtained, as the drawings have been made with
special care to that end. This fact is mentioned, as most of the plates of diatoms
published do not give correct ideas of these organisms, and are usually drawn or
engraved by persons not possessed of an intimate acquaintance with the objects
intended to be represented. The plates have been obtained by photography direct
from the author’s drawings, without the intervention of any engraver, and are, there-
fore, truthful reproductions of them.

PLAPRE oT.

Fig. 1. Front view of Zriceratium Montereyit. From the marine fossil ‘‘infusorial
stratum,” of Monterey, Cal. This figure shows the connecting membrane, which
is differently sculptured from the valves.

Fig. 2. Front view of Triceratium punctatum. In this specimen no connecting mem-

brane has been developed. From the harbor of Charleston, S. C.

3. Side view showing the valve of Pinnularia nobilis. From Germany.

4. Front view of Rhabdonema arcuatum. From the harbor of Salem, Mass.

5. Side view of Pleurosigma angulata. From the coast of France.

Fig. 6. Side view of Pleurosigma fasciola. From the harbor of New Haven, Conn.

7. Side view of Zriceratium punctatum. From Charleston, S. C.

8. Side view of Pleurosigma Balticum. From the coast of England.

Fig. 9. Side view of Pleurosigma guadratum. From the coast of England.

Fig. 10. Side view of Coscinodiscus radiatus. From the marine fossil stratum of Oran,
Algiers. In this specimen, as is very commonly the case, the radiant arrange-
ment of the markings is obscure.

Fig. 11. Side view of Mavicula didyma. From the coast of France.

Fig. 12. Side view of Zriceratium favus. From the harbor of Charleston, S. C.

Pierre “bi

Fig. 13. A specimen showing both front and side views of Gomphonema constrictum,
as well as the arrangement of the stipes or stalk. From Marion, N. J.

Fig. 14. Front view of Achnanthes brevipes, showing the flag-like appearance of the
perfect individual when attached to some submerged substance by means of its
stipes. From the coast of England.

NATURAL HISTORY OF THE DIATOMACE, 5Or

Fig. 15. Front view of a chain of two frustules of Grammatophora marina, from the
harbor of Salem, Mass.

Fig. 16. Front view of a filament of Jelosira varians, terminated by a sporangium or
seed vessel. From Englewood, N. J.

Fig. 17. Side view of Heliopelta Metzi7, from the marine fossil stratum of Nottingham,
Md. The species has been lately removed from the genus Heliofelta and placed
in Actinoptychus, and can therefore be considered as a representative of that
genus. It is one of the most beautiful of the diatoms, and has never as yet been
seen except in the fossil condition, and at the locality named.

Fig. 18. End and portion of a tube of Schizonema obtusum, from the harbor of New
York. The little navicula-like frustules of the Schzzonema are seen within the
tube.

Fig. 19. A group showing both front and side view of Synedra tabulata, from the
harbor of New York, showing the manner in which the frustules are attached to
submerged objects by means of a cushion or short stipes.

Fig. 20. A chain of Déatoma vulgare, from England, showing the front view only.

Fig. 21. Side view of Biddulphia rhombus. From the harbor of Charleston, S. C.

Fig. 22. Front view of Biddulphia rhombus, showing both valves and connecting
membrane. From the harbor of Charleston, S. C.

PRADE Akl

Fig. 23. A, B, C, D, and E, different stages of growth of Palmoglea.

Fig. 24. Lichmophora flabellata on its stipes or stalk. From the coast of England.

Fig. 25. Side view of Mavicula Barklayana. ¥rom the coast of England.

Fig. 26. Epithemia turgida, conjugating or reproducing. From England.

Fig. 27. Side view of Péznularia lata. From New Hampshire.

Fig. 28. Side view of Audlacodiscus Oregonensis. From the Sandwich islands.

Fig. 29. Side view of a Mavicula pretexta. From the Gulf of Mexico.

Fig. 30. Side view of Himantidium pectinale.

Fig. 31. Front view of a filament of Hzmantidium pectinale, from a spring near New
York.

Fig. 32. Side view of Aleridion circulare, showing the wedge-shaped frustules united
together so as to form a spiral. From West Point, N. Y.

Fig. 33. Side view of Stauronets acuta.

Fig. 34. Front view of Stauroneis acuta. From England. In these two figures the
septum, which projects like a shelf into the cavity of the frustule at the ends, can
be seen.

Fig. 35. Side view of Mavicula lyra. From Germany.

Fig. 36. Side view of Mavicula sertans. From New Hampshire.

Fig. 37. Side view of Mavicula guadrata. From Germany.

502 PHYSICAL GEOGRAPHY.

AP PENDS

NEWARK, N. J., September 1, 1874.
Prof. C. H. Hircucock, State Geologist :

Dear Sir—As you request, I send what information I can at the present time con-
cerning the specimens of diatomaceew which I have received from you or others, or
collected myself in the state of New Hampshire. The specimens have been of two
characters. For the most part they have consisted of lacustrine sedimentary deposits,
and these have been collected by yourself, or the other gentlemen connected or not
connected with the survey. A few recent gatherings have likewise been sent to me by
you, or procured by myself and a friend, in and around Hanover and elsewhere. The
lacustrine sedimentary deposits are thirteen in number, and are from the following
localities: Bemis lake, Carroll county; Bowkerville, Fitzwilliam ; Stamp Act island,
near Wolfeborough; Littleton; Laconia; Bristol; Chalk pond, Newbury ; Epsom ;
Pike’s pond, Stark; Bow; Cold pond, 2000 feet above the sea, one eighth mile from
Crawford house; Umbagog lake, Cots county; Concord. Besides these, I have
received prepared slides from Manchester and from Durham.

As it may be of interest to those who study the diatomacee to know, I will state
when and how these deposits came into my hands.

Bemis Lake. The first specimen of this deposit was sent to me by Mr. Charles
Stodder, of Boston, Mass., in 1859. I examined it and published a list of the species
I found in it at that time in the Proceedings of the Boston Society of Natural History,
May 2, 1860. This list is as follows:

Cocconema parvum.

Cyclotela Kitzingiana.

Cymbella cuspidata.

Leunotia serra.

Gomphonema acuminatum.

Limantidium gracile.

Navicula affinis; Navicula cuspidata; Navicula Jjirma; Navicula interrupta; Nav-
tcula rhyncocephala; Navicula serians.

LNitzschia 4

Pinnularia major; Pinnularia Stauronetformis; Pinnularia tabellaria; Pinnularia
wiridts.

Stauronets phenicenteron.

Surtrella biseriata; Surirella linearis.

Tabellaria fenestrata; Tabellaria flocculosa.

I have again and more carefully examined this deposit, and find that I have to make
some corrections in the above list, as well as add to it; but, as my investigation has
not been completed, I shall not at the present time make these corrections and addi-

NATURAL HISTORY OF THE DIATOMACEE. 503

tions. Besides the specimen sent me by Mr. Stodder, I received further supplies from
Mr. R. C. Greenleaf, of Boston, in 1866, and from the discoverer and owner of the
deposit, Dr. S. A. Bemis, in 1865 and 1870.

Bowkerville. The first specimens of this deposit which I received were from your-
self, in May, 1871. In the following July I visited the locality with you, and made
further collections.

Stamp Act Lsland. This deposit I received from you in September, 1871.

Littleton. The first samples of this deposit were procured from the Bailey collection
in the possession of the Boston Society of Natural History, and were sent me by Mr.
Charles Stodder. Subsequently specimens were sent to the survey by Mr. B. W.
Kilburn, and were transmitted by you to me.

Laconia. The first specimens of this I received from Mr. R. C. Greenleaf, in
November, 1865. In May, 1867, he sent me a further supply, and told me that it
occurred on a farm belonging to Col. Crockett.

Bristol. This was sent to me by Mr. C. Stodder, June, 1862, who said that he had
received it from a Mr. Webster.

Chalk Pond, Newbury. A very small sample of this deposit was sent to me by you,
October, 1871; and in June, 1874, you sent me a further supply.

“psom. This I procured from the collection of the Essex Institute, Salem, Mass.,
in December, 1864.

Pike's Pond. ‘This was discovered, I understand, by Mr. J. H. Huntington, of the
survey, and was given me by you, June, 1871.

Bow. This I also procured from the collection of the Essex Institute, and it was
labelled as having been presented by Dr. Prescott.

Cold Pond, near Crawford House. A very small sample of this was sent me by you,
July, 1872.

Concord. This I procured from the Bailey collection in Boston.

Umbagog Lake. This you sent me in July, 1870.

The slides labelled Manchester, N. H., and Durham, N. H.,1 received from Mr.
E. Samuels, of Boston, Mass.

The recent gatherings of diatomacez which I have from New Hampshire, are as
follows :

No. 1. Brook emptying into Shaker pond, Enfield.
No. 2. ‘* Muck hole,” Hanover.

. On mosses from Shaker pond, Enfield.

. Mink brook, Hanover.

. Trout pond on farm of J. E. Lawrence, Bowkerville.
. Lake of the Clouds, on Mt. Washington.

. Haystack lake.

FA
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ONAN Ew Wb

. Large pond, Bowkerville.
Nos. 9, 10, 11. Hanover.

504. PHYSICAL GEOGRAPHY.

All of these, with the exception of Nos. 6 and 7, are my collections. Nos. 6 and 7
you sent me.

Besides these gatherings, I have received fresh-water diatomacee from the following
localities in New Hampshire, through the kindness of Mr. R. C. Greenleaf, of Bos-
ton, Mass. :

Lake Mouran, on Cannon mountain, 1865.
Saco river, 1865.

Echo lake, 1865.

Profile lake, 1865.

Spring near Tip-top house, Mt. Washington, 1865.
Small pond near Crawford’s, 1865.

Spring near Lake Mouran, 1865.

Pond on Mt. Lafayette (Lake Greenleaf).
Snow arch, Tuckerman’s ravine.
Androscoggin river, Gorham.

Gibbs falls, Crawford.

Brook in Bethlehem.

In June, 1862, Mr. Charles Stodder sent me a specimen of a lacustrine sedimentary
deposit, labelled ‘‘ New Hampshire: locality and history entirely unknown; sent by
some one in Lawrence to Mr. Ordway, of Manchester, N. H.”

In Ehrenberg’s A@throgeologie, T. XXXV, A. VI, is represented a deposit of diatom-
acez said to come from Perth, N. H.[?], and this is mentioned as described in the
Transactions of the Berlin Academy for 1843. In the same work, T. XXXIII, X, is
represented another similar deposit from New Hampshire,—more particular locality
not being mentioned. This is said to be described in the 7ransactions of the Berlin
Academy for 1845. This work is not accessible to me at the present time; therefore I
am unable to give the particulars mentioned by Ehrenberg concerning them.

These, then, constitute all of the material I possess up to the present time represent-
ing the diatomacee of the state of New Hampshire, and as soon as I shall be able to
work up the forms contained in them I will transmit you a full report thereon. In the
meantime it is extremely desirable that we should receive recent collections from other
parts of the state; and I would particularly call attention to the fact that we have not,
as yet, received any gatherings from brackish or salt-water. Specimens of marine
algee encrusted with diatomacee, as they almost always are, would be particularly

acceptable. Respectfully yours,
A. MEAD EDWARDS, M. D.

NeEwARK, N. J., September 1, 1874.
Prof. C. H. H1rcucock, State Geologist :
Dear Sir—] have thought that it might prove of interest to students of the
Desmidiz to know that while making collections of diatomacez in and around Han-

NATURAL HISTORY OF THE DIATOMAEC#, 505

over, N. H., in the summer of 1871, I procured the following species belonging to that
family :

Didymoprium Borreré.

Desmidium Swartszit.

Microsterias denticulata; Microsterias crenata.

Cosmartum Botrytis.

Staurastrum polymorphum.

Docidium nodulosum.

Closterium angustatum.

Pediastrum Boryanum.

As special gatherings for obtaining these organisms were not made, the above list is
very brief; but hereafter I hope to add to it, as the desmidiz of the United States
have not been much studied, and a great deal remains to be done in our micro-zodlogy
and micro-phytology. Respectfully yours,

A. MEAD EDWARDS, M. D.

Newark, N. J., September 1, 1874.
Prof. C. H. Hrrcucock, State Geologist:

Dear Siy—During my excursions in and around Hanover, N. H., three years since,
in search of diatomacee, I collected a few specimens of wild plants infested with
diseases caused by the growth upon them and in their tissues of microscopic parasitic
fungi. These I submitted to my friend, Mr. M. C. Cooke, of London, Eng., the well

known fungologist, and he was so good as to identify them. They were the following:

LEcidium Viole, Schum., on wild violet. Vola.

Ecidium grossulari@, D. C., on wild gooseberry. bes hirtellum.
Ecidium Dracontiz, Schw., on Indian turnip. Arum triphyllum.
cidium asterum, Schw., on a plant whose name was not ascertained.

The mere announcement of the discovery of these species in New Hampshire will
not perhaps prove of interest to the majority of the readers of the survey report; and
this will arise from the fact that they will not be sufficiently informed with regard to
the important bearing these minute plants have upon the occupation of the agricul-
turist. There is no doubt that it would be greatly to the advantage of the farmer were
he better informed concerning both the animals and vegetables which prey upon his
crops. If he knew something of their habits and modes of attack, he would be the
better prepared to resist their depredations, or even to attack them in such a way as to
preserve his crops, and thus save for himself much money and labor. At some future
time, and as further specimens come into my hands, I shall take the opportunity of
transmitting to you some remarks on the fungi injurious to the crops of the agricul-
turist. In the mean time, students of these plants may be glad to know that those
I mention have been found in New Hampshire.

Respectfully yours, A. MEAD EDWARDS, M.D.
VOL i 06

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