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[EXTRACTED FRE IM SECTION ONE OF THE FISHERIES AND FISHERY INDUSTRIES
THE UNILED STATES. Pages Plates 250-259
NATURAL HISTORY OF ECONOMIC MOLLUSKS
OF THE
UNITED: STATES.
BY
ERNEST INGERSOLL and JOHN A. RYDER.
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1893.
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CUTTLES, SNAILS, BIVALVES, ETO.
By Ernest INGERSOLL.
205. THE CUTTLES—CEPHALOPODA.
The mollusks called “ Cuttles” or “‘Cuttle-fishes” bear a very important relation to the fisheries
and consequently to the food supply of the United States. It has recently been ascertained that
some of these Cuttle-fishes attain huge bulk and corresponding abilities for destruction. The two
species of Architeuthis (A. princeps and A. Harvey?), roaming through the North Atlantic and now
and then stranded upon the beaches of Newfoundland, have each a total length of from thirty to
fifty feet, and a weight of solid flesh amounting to thousands of pounds.
“The Cuttles,” says Dr. Philip Carpenter, ‘have very acute senses. They have an approach
to a brain, inclosed in a cartilaginous skull. They can hear sounds, and evidently enjoy the taste
of their food. They have a large, fleshy tongue, armed with recurved prickles, like that of the lion.
They either crawl on their head tail upwards, or swim, tail foremost, by striking with their arms,
or squirt themselves backwards by forcing water forward through their breathing funnels.
“They are ferocious creatures, the tyrants of the lower orders, and do not scruple to attack
and devour even fishes. The larger kinds are deservedly dreaded by man. Their weapons con-
sist in their powerful arms, which are abundantly furnished with rows of cup-like suckers, each
of which fastens on its prey or its foe like a limpet to the rock. Often these are accompanied with
sharp-curved teeth, strong enough to be preserved even in fossil species.”
The giant Cuttle-fishes of the north (Architeuthis) and the commoner Squids and Calamaries of
our Atlantic coast belong to the ten-armed division of the order termed Decapods. The three
smaller species ordinarily met with are Loligo Pealei, Loligo Pealet var. pallida, and Ommastrephes
illecebrosus. On the extreme southern coast they are replaced by an Octopod (Octopus granulatus).
Of these four, Loligo Pealei is the common Squid of Long Island Sound and southward, and
when full grown it is more than a foot in length. The color when living is very changeable, owing
to the alternate contractions of the color-vesicles or spots, but red and brown predominate, so as
to give a general purplish-brewn color. An allied variety or subspecies, named pallida, is a
“pale, translucent, gelatinous-looking” creature, with few spots on the back and nearly white
beneath. Commonly five or six inches long, exclusive of the arms, it frequently grows much larger,
and is of broader and stouter proportions than the type-form, from which it is further distin-
guished by its broader caudal fin and the larger size of its suckers. It belongs especially to the
western end of Long Island Sound, ‘“‘ where it is abundant with the schools of menhaden, on which
it feeds.”
“This species,” writes Verrill,! “is found along the whole coast from South Carolina to Massa-
chusetts Bay.
“Tt is the Common Squid from Cape Hatteras to Cape Cod. In Long Island Sound and Vineyard
Sound it is very abundant, and is taken in large numbers in the fish-pounds and seines, and used
to a large extent for bait. It is comparatively scarce, though not rare, north of Cape Cod. The
young were trawled by us in many localities in Massachusetts Bay in 1878. Large specimens were
taken in the pounds at Provincetown, Massachusetts, August, 1879. It was taken in considerable
5 1 Report U. S. Fish Commission, part vii, 1882, p. 355. ;
687
688 NATURAL HISTORY OF AQUATIC ANIMALS.
quantities, in breeding condition, in the fish-pounds at Cape Ann, near Gloucester, Massachusetts,
May, 1880 (var. borealis). It has not been observed north of Cape Ann. Its southern limit is not
known to me, but it appears to have been found on the coast of South Carolina.
“Tn depth, it has occurred from low-water mark to fifty fathoms. The eggs’ have often been
taken by us in the trawl, m great abundance, at many localities along the southern shores of New
England, in five to twenty-five fathoms.
“Tt is known to be a very important element in the food supply of the bluefish, tautog, sea-
bass, striped bass, weakfish, king-fish, and many other of our larger market fishes.
“Tn the Gulf of Mexico this species appears to be replaced by another species (Loligo Gahi
D’Orbigny). Of this we have several specimens, collected on the west coast of Florida, at Egmont
Key, near Tampa Bay, by Col. E. Jewett and Mr. W. T. Coons. This species is closely allied to
L. Pealei, but has a more slender form, with the caudal fin shorter and narrower in proportion to
the length of the mantle. The pen has a shorter and broader shaft, and a narrower and more
oblong blade, which has parallel, thickened, and darker-colored portions between the midrib and
margins. The tentacular suckers have their horny rings more coarsely and equally toothed, there
being only a partial alternation of larger and smaller teeth.
“ Along our southern coast, from Delaware Bay to Florida, a much shorter and relatively
stouter species (oligo brevis Blainy.) occurs, which might be mistaken by a careless observer for
the present species. In addition to its shorter body, it has very different large, tentacular suckers,
with the teeth on the horny rim coarser and all of similar form and size. Its pen is also shorter
and relatively broader, and different in structure.”
“T am not aware,” he says elsewhere,? “that any definite information has hitherto been
published as to the rate of growth or length of life of any of our cephalopods. By some writers it
has been stated that the Squids are all annual, but this seems to be a mere assumption, without
any evidence for its basis. Therefore I have for several years past preserved large numbers of
specimens of the young of Loligo Pealei, collected at different seasons and localities, in order to
ascertain, if possible, the rate of growth and the size acquired during the first season, at least.
One of the following tables (1) shows some of the data thus obtained.?
“There is considerable difficulty in ascertaining the age of these Squids, owing to the fact that
the spawning season extends through the whole summer, so that the young ones hatched early in
June are as large by September as those that hatch in September are in the following spring.
Owing to the same cause, most of the large lots of young Squids taken mm midsummer include
various sizes, from those just hatched up to those that are two or three inches long. They are
often mixed with some of those of the previous year, considerably larger than the rest. Earlier in
the season (in May and the first part of June), before the first-laid eggs begin to hatch, the
youngest specimens taken (60™™ to 100™™ long) are presumed to belong to the later broods of
the previous autumn, while those somewhat larger are believed to be from earlier broods of the
previous summer, and to represent the growth of one year very nearly.
“Taking these principles as a guide, I have arrived at the following conclusions from the data
collected :
SO Pele young Squids begin to hatch at least as early as the second week in June, on the
1TIn early summer this Squid resorts to gravelly and weedy bottoms : to lay its eggs. They are e contained i in punches
or clusters, sometimes six or eight inches in diameter, consisting of hundreds of gelatinous capsules each holding
numerous eggs. These clusters are attached to some fixed object, and the oysters upon planted beds offer conveniences
which the Squid is very likely to adopt. This occurrence seems to be a source of decided harm in Delaware Bay, for the
oystermen there assert that the larger “‘sea-grapes’’ (as they call the egg-bunches) lift many oysters from the bottom by
their buoyancy and float them off in stormy weather.—E. I.
2 Report U. 8. Fish Commission, part vii, 1882, p pp. 353~355.
3See the original article.
RATE OF GROWTH OF YOUNG SQUIDS. 689
southern coast of New England, and continue to hatch till the middle of September, and perhaps
later.
“2. By the second week in July, the first hatched of the June Squids have grown to the size
in which the body (or mantle) is 30™ to 48™™ long; but these are associated with others that are
younger, of all sizes down to those just hatched. They begin to show a disposition to go in
‘schools’ composed of individuals of somewhat similar sizes.
“3. By the second week in Angust, the largest June Squids have become 50™™ to 68™™ in
length of body, and the later broods are 5™™ to 50" long. As before, with these sizes occur others
of all ages down to those just hatched. It should be observed, however, that in those of our
tabulated lots taken by the trawl the very small sizes are absent, because they pass freely through
the coarse meshes of the net. ;
“4, By the second week in September, the June Squids have the mantle 60™™ to 82™™ long.
All the grades of smaller ones still abound. inch, or a little more than ;j5 inch. To determine the relative volumes of these
stages, and consequently’ the amount of food which has been taken in and converted into the
structure of the more advanced stage in addition to the original bulk of the egg, we need only
take the cubes of their respective diameters and compare them. Taking the diameter of the egg,
or => inch, as the diameter of the most advanced embryo seen by me, which we will consider
unity, and comparing it with {4 inch, or the transverse diameter of the newly fixed fry, we find,
after having reduced the last quantity to its simplest form as compared with 1, or the diameter of
the egg, that we have 5.1+. The diameters then of the first and last embryonic or truly larval
stages are to each other as 1 is to 5.1+, and consequently their volumes will be to each other as
the cubes of these numbers, or as 1 is to 132.651+. The difference between these two quantities,
or 131.651+ times 1, will give us approximately the amount of food material which has been taken
up by the embryo in passing from the condition when it was first able to feed until it fixed itself,
showing that the process of growth has been going on vigorously in order to augment the volume
of the young creature at the enormous rate indicated by our figures. We have, however, been
dealing not with absolute but with relative or compared volumes only; if the egg contains
ssoosuoes Cubic inch of protoplasmic matter approximately, the newly-fixed fry, which we will
assume to be globular, and contains, as shown above, over 132 times as much material, the
absolute bulk of the latter will be gsootos00 Cubic inch multiplied by 132, or s5p322550 cubic
inch, which, in its simplest form, is therefore ;gsyo7_¢ Cubic inch, or the absolute volume of the
newly fixed fry. Ninety cubed, or 729,000 young Oysters could therefore be contained in a cubic
inch of space, if taken at the stage at which they begin to be transformed into spat. This large
number is, of course, small when compared with 125,000,000, the number of eggs which might be
contained by the same extent of space.
THE LARVAL CHARACTER OF THE YOUNG OYSTER.—The proof of cine larval character of
the youngest fixed stage of the Oyster rests upon the three following well-ascertained facts:
“Ist. The perfect symmetry and great convexity of the valves; 2d. The entirely different shape
of the shell as compared with those of.the spat and adult; 3d. Its wholly different micro-
“scopic structure when compared with the later and full-grown stages. The form of the shell, at
the time the animal is about to begin to develop the spat shell, is suborbicular, very thin, ven-
; tricose, resembling in many respects the shell of Cyclas or Pisidiwm, having the symmetry of
_ those genera, with umbones of about the same form and prominence. These features mark the
larval shell of the Oyster so unmistakably that its valves may always be very readily recognized
the tips of the valves of spat under a year old. The larval valves lie on the tips of the valves
of the spat like small hemispherical caps, but can usually not be found after the young Oyster
enters upon its second year, as its umbones, together with the larval shells which surmount them,
728 NATURAL HISTORY OF AQUATIC ANIMALS.
have been eroded ‘by the action of the carbonic dioxide in solution in the sea-water. The
presence of the larval shells in an unimpaired condition on the umbones of the valves of Oysters
is therefore an indication that such specimens are young, probably under a year old.
The third character, alluded to above, which distinguishes the larval shell of the Oyster is
the perfect homogeneity of the calcareous matter. Unlike the valves of the spat or translucid
flakes from the shell of the adult, they exhibit no prismatic arrangement of the calcic carbonate
in a matrix of conchioline. In the valves of the adult and spat, on the other hand, the calcic
carbonate tends to assume a prismatic arrangement vertical or at right angles to the plane of
the length and breadth of the shell. This distinction is so marked that in very young individuals
which have only lately become fixed one may very readily determine with the aid of the micro-
scope the line of demarkation along which the formation of the larval shell ceased and where the
prismatic calcareous structure of the valves of the spat began to be developed.
CHARACTERS OF THE LARVAL SHELL.—The only characters of structure which the larval
shell has in common with that of the spat and adult are the lines of growth visible in all three.
This shows that the valves grow in extent at all stages by the addition of lime to the edges of
the valves, each layer of mineral matter and organic matrix extending over successively greater
and greater areas, as in the growth of the shells of mollusks in general, the umbones being
the points from which the valves grow in an eccentric manner in consequence of the gradually
increasing extent of the mantle—the shell-secreting organ—as the growth of the animal
proceeds. Having clearly defined the nature of the larval shell of the Oyster, up to the time
when it is ready to begin to build or secrete the shell of the spat, we may next discuss the
character of the transition from the one to the other.
The transition is apparently an abrupt one. The excessive convexity of the valves of the fry
contrast strongly with the almost flat lower valve and feebly convex upper one of the spat. At
the free edges of the larval shells where they pass directly into the structure of the valves of the
spat there is a marked offset or angle marking very distinctly the difference of convexity between
the two stages of shell development.
oop OF THE YOUNG OysTER.—As already remarked, I have seen food in the intestine
of the young Oyster on the second day of development, but how long it may take before the
young embryo of this stage of growth shall have taken and appropriated one hundred and
thirty-two times its own volume of food material, I am not able to say. This it must do
before it can have attained to the size of the larva which is transformed into spat. The food
is propelled through the alimentary canal by the action of innumerable vibratory filaments
which clothe the inside of the throat, stomach, and intestine as in the adult; the intestine,
stomach, and liver are not, however, as complex as in the full-grown animal.
Of the method of fixation I have as yet learned nothing of value. That this is accomplished
by some sort of byssus 1 have no doubt. The faet that it is the left valve which is always the
lowermost and attached one would indicate that the method of fixation was not capricious or
haphazard in its nature.
I would infer from what we learn from the study of other animals that it may require quite a
week before an embryo reaches the dimensions of one-eightieth of an ineh, but we have no data
upon which to base any conclusions of value. Of the later stage of development we know some-
thing detinitely. The main fact which we have so far decided is the size of the larval shell.
RaTkE OF GROWTH.—After fixation the growth of spat is very rapid, as may be inferred
from the fact that I have found spat upon collectors which had not been placed in position
FOOD OF THE OYSTER. 129
more than a week to ten days, upon which I detected spat one-fourth of an inch across. In
other cases the following were the observed dimensions: On a collector which had been placed
near a bed of spawning Oysters for twenty days I obtained a specimen of spat seven-sixteenths
of an inch across; from another collector immersed for forty-four days I obtained specimens
thirteen-sixteenths of an inch in diameter; from another out forty-eight days a specimen
measuring about one inch. Another set of collectors which had been out for seventy-nine days
had spat attached which measured one and three-fourths inches across. Some still larger spat
collected by me was not over eighty-two days old, and measured nearly two inches in length
from the hinge to the distal margin of the valves. Still larger specimens have been observed
by the writer, which bore every evidence of having affixed themselves during the same
season.
If we contrast the above measurements with those given by Mobius of the spat of O. edulis
of known age, I conclude that the American Oyster grows three or four times as rapidly as the
former. For instance, Mobius figures a European Oyster twelve to fifteen months old, which
measures only one and one-fourth inches in diameter. Contrasting this with the size of the
American at seventy-nine to eighty-two days old, and measuring from one and three-fourths to
nearly two inches in diameter, we see how greatly our species surpasses that of Europe in vigor
and rapidity of growth.
Of the rate of growth beyond the ages given above I have only a few data, based on the spat
which was caught on collectors put out in Saint Jerome’s Creek in July and August, 1880. In the
following autumn the collectors which had been put out into the creek were taken up and the spat
removed from them. This was then put into a box, through whieh the water could circulate
freely, and put back into the creek, in order that we might be enabled to learn how much growth
these young Oysters would make during the winter and next season. I did not have an opportu-
nity to examine them, however, until the 10th of July, 1882. From the time of their fixation in
July and August, 1880, to the time when I made my last examination of these specimens, a
period of about twenty-three months had accordingly elapsed. One of the largest specimens
examined by me measured three and three-eighths inches in length and two and five-cighths
inches in width. Another smaller specimen measured two and a half inches long and two
and a quarter inches in width. They were about the size of Oysters available for planting, and I
have no doubt that in the course of two or three years more, if placed under favorable conditions,
they would reach a marketable size. The inference, therefore, is that it takes at least four to five
years for an Oyster to grow large enough, starting from the egg, to be available for market.
In order that an Oyster may grow to attain the great size of certain single individuals which
I have seen, it may take even ten years. I should think it would take at least that length of time
for an Oyster to grow until 1ts valves would measure nine inches in length, a few of which I have
seen of this enormous size. These, it must be remembered, were not ‘Raccoon Oysters” or “‘Cat’s-
_ tongues,” as the narrow, elongate individuals are called which grow so densely crowded together
upon the banks as to be abnormally lengthened. Under favorable conditions, | do not think
“it improbable that an Oyster may live to the age of twenty years, attaining corresponding
dimensions.
\y
i . 215. THE FOOD OF THE OYSTER.
OBSERVATIONS AT SAINT JEROME’S CREEK.—The following extracts, taken mainly from
my report for 1880 to the Fish Commissioner of Maryland, will give some idea of the kinds of
organisms usually encountered on oyster banks and beds. These observations were made at
730 NATURAL HISTORY OF AQUATIC ANIMALS.
Saint Jerome’s Creek, a few miles north of the mouth of the Potomac, during the months of July,
August, September, and October: ‘
“The food of this mollusk, as is well known, consists entirely of microscopic beings and
fragments of organic matter, which are carried by currents from the palps and gills, which have
been already described, to the large mouth of the animal at the hinge end of the shell. The inside
of the gullet and stomach, like some other parts of the body, are covered with cilia, so that food
once fairly in the mouth will be carried by their action down to the cavity of the stomach, where
it is carried into the folds and deep pouches in its walls, and even into the openings of the bile
ducts, to undergo digestion or solution, so as to be fitted in its. passage through the intestine to
be taken into the circulation, and finally disposed of in building up the structures of the body.
“Along with the food which is taken, a very large amount of indigestible dirt, or inorganic
matter, is carried in, which, in a great measure, fills up the intestine, together with the refuse or
waste from the body. This material, when examined, reveals the fact that the Oyster subsists
largely on diatoms, a low type of moving plants which swim about in the water, incased in minute
sandstone cases, or boxes, of the most delicate beauty of workmanship. These, when found in
the intestine, have usually had their living contents dissolved out by the action of the digestive
juices of the stomach. I have found in our own species of Oyster the shells of three different
genera of diatoms, viz: Campylodiscus, Coscinodiscus, and Navicula. The first is a singularly bent
form; the second is discoidal; and the last boat-shaped, and all are beautifully marked. Of
these three types, I saw a number of species, especially of the latter, but as I was not an authority
upon the systematic history of any of them I had to neglect the determination of the species. No
doubt many more forms are taken as food by the Oyster, since I saw other forms in which the
living matter inside the siliceous cases was brown, the same as in most of the preceding forms
which I have indicated. Some of these brown forms were so plentiful as to color a considerable
surface whereon they grew of the same tint as themselves.
‘“‘ Besides the diatoms and the spores of alge, the larve or young of many animals, such as
sponges, bryozoa, hydroids, worms, mollusks, are small enough to be taken in as aliment by
the Oyster, though their bodies in most cases being soft and without a skeleton, it is impossible
to find any traces, either in the stomach or intestine, of their remains, to indicate that they have
formed a part of the bill of fare of the animal. What, however, demonstrates that such small
larval organisms do help to feed the Oyster is the fact that at the heads of the small inlets o1
creeks along the Chesapeake, where the water is but little affected by the tides and is somewhat
brackish and inclined to be stagnant, there always appears to be a relatively greater development
of a somewhat characteristic surface or shallow water fauna of minute forms.
“In Saint Jerome’s Creek the microscopic fauna of its headwaters is entirely different from
that of the body of the creek; two minute forms inhabit in vast numbers the former, while I
sought in vain for them in the more open and changeable waters of the main body of the inlet,
which are brought into active movement twice a day by the action of the tides. One of these
forms, an infusorian,! one twenty-fifth of an inch in length, was found covering every available
surface of attachment, so that countless multitudes of the naked young would be swimming about
in the water previous to building the curious spiral tubes which they inhabit—admirably fitted in
this state as food for the Oyster. Besides the type referred to, there were a number of other
infusorians, which in their so-called swarming stages of development would become available
as Oyster food. Of such a pes I noticed four different itigiai 4 either belonging or very nearly §
‘On the occurrence of Freia producta, Wright, i in the LOhcen bake Bay.—Am. Naturalist, , 1880, pp. 810, 811.
LOCATION OF OYSTER BEDS. 731
related to the genus Cothurnia; all of the forms built tubes for themselves. I also noticed several
forms of bell animalcules, the swarmers of which would become available as food for the Oysters
lying in the vicinity.
“The diatoms did not seem to me to be more abundant in the headwaters than in the open creek.
There was one moss animal of remarkable character, which I found in the headwaters only. This
creature was very abundant, and no doubt its embryos, like those of the infusoria referred to, were
available as food. ;
“Of free-swimming infusorians, I noticed a number of genera; one especially attracted my
attention from its snake-like appearance and singularly rapid contortions; it had a tuft of vibrating
hairs or cilia at the head end in close relation with the mouth. Another more abundant type was
the curious genus Huplotes, with a thick shell inclosing the soft protoplasm of the body; the latter
was of an oval form, flat beneath and rounded on the back, so that the resemblance when the
large foot-like cilia were in motion, carrying the animal about, was strikingly like a very minute
tortoise, the resemblance being heightened when the animal was viewed from the side.
*Rod-like alg of minute size, the larve of crustacea, especially the vast numbers of extremely
small larval Copepoda, must enter as a perceptible factor into the food supply of the Oyster.
‘« There is no doubt but that the comparatively quiescent condition of the headwaters of these
inlets and creeks, available as oyster-planting grounds, are more favorable to the propagation of
minute life than the open bay or creeks, where the temperature is lower and less constant. Prac-
tically, this is found to be true, for oystermen seem to be generally agreed that Oysters ‘fatten’
more rapidly, that is, feed more liberally in the headwaters—blind extremities of the creeks—than
elsewhere. This notion of the oystermen is in agreement with my own observations during the past
year. Oystermen also assert that Oysters ‘fatten’ more rapidly in shallow waters than in deep
ones, a point upon which I made but few observations; but such as I did make tended to confirm
such an epinion. In illustration I may contrast the condition of the Oysters in the pond leased by
the commission at Saint Jerome’s and those dredged off Point Lookout, in twenty or thirty feet of
water, on the 3d day of October, 1880. The Oysters in the pond, by the middle or end of September,
were in good condition as to flesh, and marketable, while those from deeper water off Point Lookout,
and but little later in the season, were still extremely poor, thin, and watery, and utterly unfit for
market. These differences in condition, it seems to me, are to be attributed in a great measure to
differences of temperature and the abundance of food, but mainly to the latter.”
These observations give us some hints regarding the advantages arising from the cultiva-
tion of Oysters in more or less stagnant water, in which, as in the French parks or claires, an
abundance of microscopic life would be generated in consequence of a nearly uniform temperature,
higher in the early autumn months at least than the waters of the open sea, where cold currents
also would tend to make it still less uniform and thus interfere with the generation of the minute
food of the Oyster. In other words, it would appear that the effect of the French method is to
furnish the best conditions for the rapid and constant propagation of an immense amount of
microscopic food well adapted to nourish the Oyster. That unlike Oysters exposed to a rapid flow
of water on a bottom barren of life they grow and quickly come into a salable condition.
SITUATIONS BEST ADAPTED FOR OYSTER CULTURE.—In this country narrow coves and
inlets with comparatively shallow water appear to furnish the best conditions for the nutrition
and growth of Oysters; and according to my own experience these are the places where we act-
ually find minute animal and vegetable life in the greatest abundance, and, as might have
been expected, the Oysters planted in such situations appear to be in good condition early in
the autumn, long before those which are found in deeper and more active water, where their
732 NATURAL HISTORY OF AQUATIC ANIMALS.
food has less chance to multiply. If the French mode applies successfully to an inferior species,
ours, which grows so much more rapidly, ought to derive a proportionally greater benefit from
being treated in the same manner. However, before we are ready to deal with the material
on which the Oyster feeds, we desire a more perfect acquaintance with the microscopic life
which grows upon oyster-beds and swims about in the adjacent waters. From the fact that
the lower forms of life in fresh water often appear in great abundance one year, while in the
next, from some unexplained cause, none of the same species will be found in the same situation,
we may conclude that similar seasonal variations occur in the phases of the microscopic life of
a given oyster-bed and its vicinity. |
INFLUENCES OF ENVIRONMENT.—Such yearly variations in the abundance of microscopic
life are probably the causes of the variable condition of the Oysters taken from the same beds”
during the same season of different years. Violent or sudden changes of temperature are prob-
ably often the cause of the destruction of a great amount of the minute life upon which the Oyster
feeds. Backward and stormy seasons doubtless also affect the abundance of the microscopic life
of the sea. All of these questions have, however, as yet been scarcely touched, and, judging from
the disposition of many of our students of zoology to be content merely with a description of new
species and the compilation of lists, instead of also entering into investigations of the life-histories,
the relative abundance of individuals, and the influence of surrounding conditions upon the
forms they study, it will take some time yet before we get the information so much desired.
When we arrive at this knowledge we will know why it is that Oysters taken from a certain bed
are in good condition for a season or two and then for one or more years are found to be watery and |
of poor quality, as well as why it is that the Oysters of certain beds, which for years have had a_
high reputation for their fine qualities, are suddenly found to be more or less green in the beard, |
as I have been informed is now the case with the Oysters of Lynn Haven Bay, Virginia. |
As to the influence of brackish water in improving the condition of Oysters, let me observe ;
here that those who hold to that opinion appear to forget to bear in mind that brackish-water beds |
are often in the case just described; that lying in shallow, relatively quiet water, an abundance
of food is generated which is rapidly consumed by the animals, quickly bringing the latter into
condition, the brackish state of the water getting the credit of the result.
“Tn a paper published in the report to the British Government on oyster-culture in Ireland,
in 1870, Prof. W. K. Sullivan, of Dublin, remarked that independently of the mechanical constitu-
tion of the shore and littoral sea-bottom, 7. e., deposition of sediment, the currents, the temperature,
etc., the nature of the soil produces a marked influence upon the food of the plants and sedentary
animals that inhabit the locality, as well as upon the association of species. Especially is it the
case with Oysters, that the soil exerts so much influence on the shape, size, color, brittleness of
shell, and flavor of the meat, that an experienced person can tell with great certainty where any
particular specimen was grown.' . . . Were we able to determine the specific qualities of
tne soil which produce those differences in the qualities of Oysters, it would be an important step
in their cultivation. Again, soils favorable for the reproduction of the Oyster are not always
equally favorable for their subsequent development; and, again, there are many places where |
Oysters thrive but where they cannot breed. This problem of the specific influence of the soil is,
however, a very difficult and complicated one. First, because it is almost impossible to separate
the specific action of the soil from that of the other causes enumerated ; and next, because, though
much has been written on the subject of Oysters, I do not know of any systematic series of experi-
1E. INGERSOLL: Report on Oyster Industry, Tenth Census.
PROTOZOANS OF SAINT JEROME'S CREEK. 733
ments carried out upon different soils, and for a sufficient length of time to enable accidental
causes to be eliminated, which could afford a clue to the determination of the relative importance
of the action of the several causes above enumerated at the different stages of development of the
Oyster. . . . I believe the character and abundance of Diatomacea and Rhizopoda, and other
microscopic animals, in Oyster-grounds, is of primary importance in connection with Oyster
cultivation. The green color of the Colchester and Marennes Oyster shows how much the quality
may be affected by such organisms. It is probable that the action or influence of the soil of Oyster-
grounds upon the Oyster, at the various stages of its growth, depends mainly upon the nature and
comparative abundance of the Diatomacea, Rhizopoda, Infusoria, and other microscopical organisms
which inhabit the ground. I have accordingly always noted whete the mud appeared to be rich in
Diatomacea, Foraminifera, and other microscopic organisms. A thorough a study of a few differently-
situated Oyster-grounds, exhibiting well-marked differences in the character of the Oyster from
this point of view, by a competent microscopist, acquainted with the classes of plants and animals
just mentioned, would be of great scientific interest and practical importance.”
PROTOZOANS OF SAINT JEROME’S CREEK.—The Protozoan fauna of Saint Jerome’s Creek
presents considerable variety; several species of test-building Cothurniw were noticed, one
Vaginicola, three species of Vorticella or bell-animalcules, free-swimming Puplotes, Nassula; of
the latter type an exceedingly elongate form was noticed, with a body almost as slender as a
thread-worm. Monads were noted sometimes in profusion, though some of these may have been
the spores of alge. Ameceboid forms were very few, and the only one which was frequently
noticed was a form so nearly like Actinophrys sol that I would pronounce it the same.
The Freia producta Wright was most common; this creature is related to the fresh-water
trumpet animalcules, and is one of the most beautiful Protozoans I have ever seen. I reproduce
here, with some changes, my description of the Chesapeake form from the ‘‘ American Naturalist”
for November, 1850:
“The tubes in which the animalcule resides are formed of a narrow transparent ribbon of
horny consistency, wound into a spiral and terminating in a trumpet:shaped extremity, from which
the odd peristome of the inhabitant protrudes. The basal or attached end is usually bent at an
angle to the tube and bears a striking resemblance to the foot end of a stocking resting upon the
sole. This portion is not composed, like the tube, of a spiral ribbon, but is simply a thin-walled
sac, from the open end of which the ribbon takes its rise, but it is composed of the same kind of
material. Many of the tubes show a trumpet-like rim projecting from the sides of the former, a
little above the middle, and of the same form as the terminal rim, showing that this, like the form
described by Mr. Wright from British waters, may stop building its tube for a time and then
recommence.
“The adult animal, tube and all, when fully extended, will measure one twenty-fifth of an
inch in length. It is of the same color as Stentor ceruleus, or bottle-green, but has the power of
elongating and twisting itself as greatly as S. reseli. The peristome is quite unlike that of Preia
ampulla and bears a strong likeness to the blades of a pair of obstetrical forceps. The blades are
deeply grooved, forming a deep ciliated demi-canal with parallel sides, and at the junction of their
bases lies the spacious, twisted, and spirally ciliated pharynx, which is bounded dorsally and
ventrally by the prominent folds which unite on either side with the long, curved lobes of the
peristome. There is a small basal disc as in Stentor, and the ectosarc is traversed as in that genus
by parallel granular bands, regarded as muscular fibers by some writers. The usual food-balls
and vacuoles are present, and I was enabled to define sharply the endosare from the ectosarc,
734 NATURAL HISTORY OF AQUATIC ANIMALS.
and clearly see the nucleus. The tube or ribbon-secreting organ described by Wright I was unable
to discover. :
“ When fully extended the basal portion of the animal becomes attenuated to a thin bluish
filament, which widens towards the peristome, where the body is over half as thick as the inside
diameter of the tube. When fully retracted and resting, the animal resembles in its oblong shape
a retracted and resting Stentor, and measures about = as long as when fully extended. The
ribbon which forms the tube makes from four to twenty-four turns in specimens of different ages.”
This organism I since find to be an inhabitant of the bay also, but is not so abundant as in
the creek. Small mica collectors fixed to floating corks in the hatching jars and aquaria used
during the past season were found to afford a nidus for Freia as well as Zodthamnium, the latter
multiplying at a most astonishing rate in a very few days. Under similar conditions, amoeba,
apparently A. proteus, multiplied at a suprising rate; this was the case, too, with a small brown
diatom which would coat in three or four days the sides of the glass vessels with a thin brownish
film composed of countless myriads of individuals of the one species. The temperature of the
bay-water used in the aquaria at this time would range from 76° F. to 89° F. The Vorticellide
also soon attach themselves, and next to the hypotrichous infusorians found in the locality are the
most important animalcular forms found in the Chesapeake. At the mouth of the Cherrystone
River I last year found Licnophora cohnii in great abundance ectoparasitic upon an unidentified
hydroid. The heliozoén, Actinophrys sol, is found in the bay and Saint Jerome’s Creek, and I think
it capable of swallowing dead or enfeebled Oyster eggs and embryos.
MUTUAL RELATIONS BETWEEN THE OYSTER AND ITS PREY.—MObius calls an Oyster-
bank a Biocenosis or interdependent community of life. The many species of animals found
on the banks and beds are no doubt more or less mutually dependent upon each other for
subsistence, but this is perhaps not any more true of Oyster-banks than it is of terrestrial
faune. There are no doubt vast numbers of floating embryos of Oysters eaten by other
animals growing on the beds which bring their food supply to themselves by means of
currents produced by ciliary motion. On the other hand, there are no doubt vast numbers of the
minute swimming embryos of these, drawn in and swallowed by the Oyster, which may, indeed,
for aught we know, in this way swallow many of its own young, for the current produced by the
Oyster by means of the cilia clothing its gills is by no means a feeble one, though it is exceeded
in power by the current flowing into and out of the siphons of Mya. In the latter I have frequently,
upon opening the animal, found several Copepoda plainly visible to the naked eye swimming
about in the water in the inferior mantle cavity, which had evidently been drawn in by the inward
current. It is plain in this case that very mild means may become effective as prehensile and
destructive agents, so as to bring remotely related types into intimate vital relations.
Though an animal may be apparently invulnerable on account of the effectiveness of its
covering, it cannot emancipate itself from the abiding struggl« it has to make to obtain food, no
matter how passively it may appear to conduct itself. The Oyster has such a character, yet it has
been apparent from what has been observed before, that it is entirely dependent for a vigorous
existence upon the favorableness of surrounding conditions. The beds and banks in a true sense
are interdependent communities, whose vigor may no doubt be impaired by the removal of a single
one of its members. Suppose we should take away the algw, diatoms, Oyster-crabs, vibriones,
bacteria, infusoria, in fact all the minute life; we should greatly impair if not destroy the vitality
of the beds. While it is true that many of even the smallest forms may destroy food which
should propertly be consumed by the Oyster, that were it not for the presence of these same small
forms some destructive element might attain such a development as to be more injurious still.
CAUSE OF THE GREEN COLOR OF THE OYSTER. 735
There is therefore no doubt but that a delicate balance of power is maintained by these rivals
which is best for the health of the community. The stability of permanent oyster-beds, it must
be remembered, furnishes the right conditions for the survival of many types. It is a place where
they find both a home and plenty of food. It is the very favorableness offered by these places
which tends to induce them to congregate and multiply, and it becomes a serious question whether
the artificial establishment of banks will not in time cause the proper types to congregate and
multiply so as to afford the needed food supply for the Oysters. That destructive members of the
community may also be attracted is admitted, but if the beds are established in shallow waters, as
I have previously suggested, the destruction of such unwelcome intruders may be very readily
effected. ‘ Drills” and boring-sponges are naturally to be thought of as types which should be
destroyed, while diatoms, infusoria, small polyps, bryozoa, minute alge, etc., are to be favored in
every way. Those forms again which the oyster-culturist knows are only there for the purpose
of getting a good living with little trouble to themselves ought to be destroyed.
Tt might be an advantage to introduce certain desirable forms onto a bank, which might be
supposed to be useful as afood supply. Infusoria and diatoms not previously existing might be
introduced in this way; this, I think, would be especially easy in the case of the former where
the type was one which is fixed during its adult life.
216. ON THE CAUSE OF THE GREEN COLOR OF THE OYSTER.
EXPERIMENTS AT WASHINGTON. AND PHILADELPHIA.—I have frequently read accounts of
Oysters which had become green-fleshed in certain localities, and it has also been asserted that
competent chemists had discovered poisonous green substances of metallic origin in such speci-
mens. Tests made at the Smithsonian Institution by Professor Endlich in 1879 failed to disclose
anything poisonous in some green Oysters which had excited the suspicion of the Board of Health
of the city of Washington. This investigator, it is desirable to state, resorted to every test known
to him in order to discover if anything poisonous was present, and failing to discover any harmful
substance concluded that the color must be due to some inert material. In order to see if the color
was due to the presence of some green compound of copper, Prof. H. C. Lewis, of the Academy of
Natural Sciences of Philadelphia, kindly made some delicate tests for me, using small dried frag-
ments of an Oyster very deeply tinged with green in various regions, especially in the liver, con-
nective tissue, and mantle. The fragments were burned in a bead of microcosmic salt and chloride
of sodium on a clean platinum wire in a gas flame; this test did not give the characteristic sky-
blue flame which should have been developed had there been the minutest trace of copper present.
It is therefore clear that the substance, whatever it may be, is not a corrosive metallic poison
derived from copper, which if present would almost undoubtedly be detected by a peculiar acrid
metallic taste, which would be experienced when one ate such Oysters. In making some practical
tests as to the relative qualities of such Oysters as compared with white-fleshed ones, oppor-
tunities for which were kindly furnished me by Mr. J. M. Carley, of Fulton Market, I failed to
detect the slightest difference of flavor. Such also is Professor Leidy’s verdict, who informs
me that he made a similar experiment, and a restaurateur, with whom I discussed the matter,
declared that he was in the habit of selecting them for his own eating, preferring their flavor to
that of the white Oysters.
VARIATIONS IN COLOR.—If it be objected that the green color indicates an unhealthful
condition of the animal, it may be stated that other color variations of the flesh have fallen
736 NATURAL HISTORY OF AQUATIC ANIMALS.
under my observation recently. What is now alluded to is the yellowish, verging toward
a reddish cast, which is sometimes noticed in the gills and mantle of both the American and
European species. This, in all probability, like the green color, is due to the reddish-brown
matter which is contained in much of the diatomaceous food of the animal.
Mr. J. M. Carley has also called my attention to these variations, and was inclined to attribute
them to the soil in the vicinity of the beds. But if the classical writers are to be trusted, to the
green, yellow, and white fleshed sorts we must add red, tawny, and black fleshed ones. Pliny
tells us of red Oysters found in Spain, of others of a tawny hue in Illyricum, and of black
ones at Circeii, the latter being, he says, black both in meat andshell. Horace and other writers
awarded these the palm of excellence.—(O’Shaughnessy.) However, the black appearance may
only have been due to an abundance of the natural purple pigment in the mantles of the animal,
which varies very much in different forms; some, judging from the dark purple color of the whole
inside of the shell, must have the whole of the mantle of the same tint. The amount of color in
the mantle, especially at its border, varies in local varieties of both the American and European
species, as may often be noticed.
Sometimes almost the whole of the outside surface of the mantle is charged with dark purple
pigment cells. That copper is not usually the cause of the green color of Oysters I also have the
additional testimony of Prof. W. K. Sullivan, of Dublin, who says:
“As the green color of the mantle of Oysters from certain localities just referred to is
commonly attributed to copper, and as such Oysters are consequently believed very generally to
be poisonous, and their value therefore greatly depreciated, [ made the most careful search for
traces of that metal in the muds which I had received from grounds known to produce green-
bearded Oysters. Oysters and other mollusea placed in solutions containing copper and other
metals absorb them and retain them in their tissues. I have had two or three opportunities of
examining Oysters which had assimilated copper, owing to mine-water containing it being allowed
to flow into estuaries at places close to oyster-beds. In cvery case the copper was found in the
body only of the Oyster, which it colored bluishg-reen, and not in the mantle or beard, which was
not green. In the green-bearded Oysters which I have had an opportunity of examining, the body
was not green, and no trace of copper could be detected in any part of the animal. The color,
too, was not the same as that of the true copper Oysters, but rather that which would result from
the deposition of chlorophyl or other similar chloroid vegetable body in the cells.”
The American consumer, however, need not be alarmed about the presence of copper im our
species, as there are no beds on our eastern coast into which the washings from mines ever flow,
as we have no workable deposits of copper near any of our beds, as in Cornwall, England. Besides,
Iam inclined to doubt the statement of Professor Sullivan that Oysters or other mollusks can
absorb copper salts until their tissues are “colored. bluish-green.” Every competent histologist
knows how very readily organisms are killed by the action of inorganic acids and salts, several of
which are constantly used by biologists in fixing histological characters. Liebig, in his “* Animal
Chemistry,” long ago pointed out that the oxides and metallic compounds of antimony, arsenic,
copper, and lead had a very remarkable affinity for protoplasm, producing its immediate death.
In consequence, he suggested a very high chemical equivalency for living matter. This has since
been confirmed by the studies of Loew and Pokorny, who found that silver nitrate would produce
a reaction with protoplasm if diluted to the extent of one part to a million of water.
PROBABLE CAUSE OF THE GREEN COLOR.—It is highly probable that the green color of the
Oyster is due to the absorption from its food of a harmless vegetable pigment. In this country
green-bearded Oysters occur at Lynn Haven Bay, Hongers and York ivers, Virginia, on the
t
OBSERVATIONS OF GAILLON AND JOHNSTON. Tone
coast of New Jersey, in New York Bay, and Long Island Sound. I have seen specimens from a
number of these localities, and also tasted them both raw and cooked without being able to detect
any disagreeable or apparently harmful flavor.
Diatoms and green alge occur in great abundance in the stomach of the Oyster, especially the
former. The intestine is sometimes packed with countless numbers of the empty frustules or tests
of diatoms, mixed with dark, muddy ooze or sediment and very fine particles of sand or quartz.
It has been objected that the green color could not be derived from diatoms, because these organ-
isms are, aS a rule, apparently brown rather than green. This objection I find to be based upon
a misapprehension of the structure of the Diatomacee, as may be gathered from the following
general statement taken from Sachs’ ‘Text Book of Botany,” one of the latest and highest
authorities. On page 222 he says: ‘The diatoms are the only alge except the Conjugate in which
the chlorophyl occurs in the form of disks and bands, but in some forms it is also found in grains,
and the green coloring matter is concealed, like the chlorophyl grains in Fucacew, by a buff-colored
substance, diatomine or phycoxanthine.” It appears, then, according to the foregoing quotation,
that it is not impossible for diatoms to be the cause of the green tint in Oysters, which, let me
remark, is very nearly that of some pale green forms of those organisms which I have observed in
water from oyster coves where I have conducted microscopic studies. Both green and brown
diatoms may frequently be found in the stomach, and in making examinations to discover them I
find it best to thrust the nozzle of a pipette directly into the stomach through the mouth and
esophagus. The pipette should have a compressible bulb, so as to enable one to draw up the
contents of the gastric cavity into the tube without injuring the animal or taking up any fragments
of it to vitiate the experiment.
OBSERVATIONS OF GAILLON AND JOHNSTON.—Speaking of the abundance of the Navicula
ostrearia of Kiitzing, M. Benjamin Gaillon, in 1820, said that they inhabit the water of the
tanks or “ parks” in which the Oysters are grown in such immense abundance, at certain seasons
of the year, that they can only be compared to the grains of dust which rise in clouds and
obscure the air in dusty weather. Dr. Johnston, speaking of the French Oysters, says that in
order to communicate to them a green color, which, as with us (in England), enhances their
value in the market and in the estimation of the epicure, they are placed for a time in tanks
or “parks,” formed in particular places near high-water mark, and into which the sea can be
admitted at pleasure by means of sluices; the water being kept shallow and left at rest is
favorable to the growth of the green Conferve and Ulve; and with these there are generated
at the same time innumerable crustaceous animalcules which serve the Oysters for food and
tincture their flesh with the desirable hue.
This last remark of Dr. Johnston’s at first struck me as improbable, but I have met with great
numbers of small crustaceans, Copepoda mainly, in the branchial cavity of the common Clam (Mya
arenaria). Certain peculiar species have also been described by Allman from the branchial
cavities of ascidians. More recently, while investigating the contents of the stomach of the
Oyster, by the method already described, I find that it also swallows crustaceans, which are digested
and absorbed as food. The tests of nauplii or very minute’ larval crustaceans with the contents
digested out were frequently met with. Doubtless many very small Copepoda are also swallowed
and digested, but these are not green. Besides the foregoing, [ sometimes met with the very young
Shells of larval gasteropods and lamellibranchs; indeed, it is not improbable that the adult Oyster
may consume its own larve. The remains of bryozoa were also observed, such as Pedicellina
americana. The test of a peculiar elongate rhizopod and the cephalula stage of several worms
were also noticed. Of the smaller organisms usually associated with more or less clearly marked
47 F
738 NATURAL HISTORY OF AQUATIC ANIMALS.
putrefactive changes, one which I find almost uniformly present is a filiform or thread-like organ-
ism allied to Spirillum. It, however, was always found in the stomach in great abundance, and
especially in the pyloric portion of the intestine in which the crystalline style is lodged. This
organism is probably harmless; a similar one is frequently found in both fresh and salt water,
and has at times been developed in prodigious numbers in the reservoirs from which the supplies
of water were drawn for a large city, without any evidence of its having produced a harmful
effect upon those who drank of the water.
Vibws oF Lerpy, PUYSEGUR, AND DECAISNE.— Professor Leidy, at a recent meeting of
the Academy of Natural Sciences of Philadelphia, stated it as his belief that Oysters feed at
times on the zoospores of certain alge, as those of Ulva latissima (sea cabbage), which he knew
from personal observation to be green, and which he thought might possibly be the cause of
the green coloration of the soft parts of the animal as sometimes observed in certain localities.
Very possibly this may be the case, but judging from what I have seen and heard from oyster-
men, as well as from what I have read in various publications relating to this matter, I am not
inclined to regard this as the only source of the unusual green tint of the flesh of the Oyster.
I hope to be able to show that it is probably of vegetable origin, and therefore quite harmless.
That it is not copper we may be equally certain, as Professor Lewis’ tests have shown, for
any such quantity of a copper salt as would produce the green gills, heart, and cysts in the
mantle, such as are often observed, would, without doubt, be as fatally poisonous to the Oyster
as to a human being. The source of the green has recently been investigated by two French
savants, MM. Puysegur and Decaisne, who found that when perfectly white-fleshed Oysters
were supplied with water containing an abundance of a green microscopic plant, the Navicula
ostrearia of Kiitzing, their flesh acquired a corresponding green tint. These investigators also
found that if the Oysters which they had caused to become imbued with this vegetable green
were placed in sea-water deprived of the microscopic vegetable food the characteristic color would
also disappear. Whether this will finally be found to be the explanation in all cases remains to
be seen, as some recent investigations appear to indicate that it is possible that a green coloration
of animal organisms may be due to one of three other causes besides the one described above as
the source of the green color of the Oyster.
GEDDES UPON CHLOROPHYL-CONTAINING ANIMALS.—Patrick Geddes, in a recent number
of “ Nature,” has pointed out that the “list of supposed chlorophyl-containing animals
breaks up into three categories: first, those which do not contain chlorophyl at all, but green
pigments of unknown function (Bonellia, Idotea, etc.); secondly, those vegetating by their own
intrinsic chlorophyl (Convoluta, Spongilla, Hydra); thirdly, those vegetating by proxy, if one may
so speak, rearing copious alge in their own tissues, and profiting in every way by the vital
activities of these.” This latter is one of the most interesting and important of modern biological
discoveries, that living animal bodies may actually afford a nidus for the propagation of green
microscopic plants and not be injured but rather be benefited thereby. The oxygen thrown
off by the parasitic vegetable organism appears to be absorbed by the tissues of the animal host,
while the carbonic-acid gas thrown off by the latter is absorbed by the vegetable parasite, thus
affording each other mutual help in the processes of nutrition and excretion. This singular
association and interdependence of the animal host and vegetable guest has received the some-
what cumbrous name of Symbiosis, which may be translated pretty nearly by the phrase “asso-
ciated existence.” This is not the place for the discussion of the purely scientifie aspect of this
question as already ably dealt with by Dr. Brandt, Patrick Geddes, Geza Entz, and others, and
THE GREEN MATTER IN ANIMALS. 739
we will therefore only notice their researches in so far as they appear to have a bearing upon
the origin of the green color of the Oyster.
ENT’ DISCOVERIES.—Entz has discovered that he could cause colorless infusoria to become
green by feeding with green palmellaceous cells, which, moreover, did not die after the death of
their hosts, but continued to live, growing and developing within the latter until their total evolu-
tion proved them to be forms of very simple microscopic green algw, such as Palmella, Gleocystis,
etc. My own observations on some green-colored infusorial animals have been of so interesting a
character that I will here describe what I observed in a green bell animaleule ( Vorticella chloro-
stigma). Upon investigating their structure, I found that next the cuticle or skin in the outer soft
layer of their bodies, known as the “ectosare,” at all stages there was a single stratum of green
corpuscles very evenly or uniformly imbedded. In another form (Stentor), as already noticed by
Stein, the same superficial layer of green corpuscles was observed, reminding one very forcibly of
the superficial layer of chlorophyl grains observed in the cells of some plants, as, for instance,
Anacharis. Now, it is well known that certain animalcules are at times quite colorless and at
others quite green; this appears to be the case with Ophrydium. In this last case I have a
suspicion that vegetable parasites may be the cause of the green variety, but as for the others,
Stentor and Vorticella, I am not so sure that their green forms are so caused. In them the
superficial positions of the green corpuscles and their behavior toward reagents lead me to
think that they must be regarded as integral parts of the creatures in which they are found.
NATURE OF THE GREEN MATTER IN ANIMALS.—A grass-green planarian worm (Convoluta
Schultzit), found at Roscoff by Mr. Geddes, was observed by him to evolve oxygen in large
amounts, like a plant, and “both chemical and histological observations showed the abundant
presence of starch in the green cells; and thus these planarians, and presumably, also, Hydra,
Spongilla, etc., were proved to be truly vegetating animals.” While some organisms, like the
foregoing, appear to have true chlorophyl grains imbedded superficially in their own substance,
others, like the radiolarians, some siphonophores, sea anemones, and jelly-fishes, harbor true
vegetable parasites, or, preferably, vegetable guests.
That the green observed in a number of animal organisms is of the nature of chlorophyl,
or leaf green, has been proved by Lankester by means of the spectroscope. A. W. Bennett, in
alluding to Lankester’s observations, says: “In all cases the chlorophylloid substance agrees in
having a strong absorption band in the red—a little to the right or left—and, except in Zdotea, in
being soluble in alcohol, and in having strong red fluorescence, and in finally losing its color when
dissolved.”
The vegetable organisms which have been found to inhabit the lower forms of life alluded to
in the foregoing paper have been regarded as belonging to two genera, which Dr. Brandt has
named Zodchlorella and Zoébxanthella, and which are probably in part synonymous with the genus
Philozoon, afterwards proposed by Mr. Geddes. The latter gentleman, however, claims to have
first demonstrated the truth of the view that the yellow cells of radiolarians and polyps are alge;
Secondly, the foundation of the hypothesis of the lichenoid nature of the alliance between alge
and animal into a theory of mutual dependence; and, thirdly, the transference of that view from
the region of probable speculation into that of experimental science.
Hitherto no one has apparently noticed the occurrence of green vegetable parasites in
divalve mollusks except Professor Leidy, who has very kindly permitted me to use the facts
observed by him relating to Anodon, one of our common fresh-water Mussels. In this animal he
some years ago observed what must be considered to be algous parasites. He found them in
great numbers infesting the tissues of the Mussel and of a larger size than the nuclei of the cells of
the host in which they were imbedded. They were also provided with a nucleus, and were, there-
740 NATURAL HISTORY OF AQUATIC ANIMALS.
fore, not a part of the animal but a distinct vegetable organism. These facts, observed a long
time since, render it very probable that Professor Leidy was one of the first to notice the intra-
cellular parasitism of a plant in an animal.
The green color of the Oyster, as far as my experience goes, is not intense, as in Inany green
animals, such as we observe in Stentor, Spongilla, Hydra, ete., but is a pale pea-green tint. This
has been found to be the color of affected natives as well as of foreign ones, the gills and mantle
being usually most distinetly tinged. Exceptionally the heart is affected, its color sometimes
being quite intense.
EXPERIMENTS UPON EUROPEAN OystERS.—In studying some Oysters which were obtained
from England through the kind offices of Messrs. Shaffer and Blackford, in response to a request
coming from Professor Baird, certain ones were found which were decidedly green. Of these the
French specimens of Ostrea edulis, and a very singular form, labeled ‘‘ Anglo-Portuguese,” had the
gills affected, and in some of the latter the liver, heart,and mantle were very deeply tinged in
certain parts, so much so that I decided to make as critical an examination as my resources could
command.
Spectroscopic investigations gave only negative results, as it was found impossible to discern
any positive evidence of chlorophyl from the spectrum of light passed through thin preparations
made from specimens of green-tinted Oyster, some of which, like those made from the heart, are
decidedly green to the naked eye. There was no absorption noticed at the red and blue ends of
the spectrum, such as is observed when the light which enters the slit of the spectroscope first
passes through an alcoholic solution of leaf green or chlorophyl; indeed, the spectrum did not
appear to be sensibly affected by the green substance which causes the coloration of the Oyster.
No attempt was made to test the matter with the use of alcoholic green solutions obtained from
affected Oysters, as the former are not easy to get with a sufficient depth of color, because of the
relatively small amount of coloring matter present in the animals. Unstained (fresh) preparations
were used in all of these experiments.
COLORS IN DIFFERENT PARTS.—I find the liver to be normally of a brownish-red color in
both the American and European Oyster, sometimes verging toward green. When the flesh or
gills of the animal is green, the liver almost invariably partakes of this color, but in an intensi-
fied degree. The green stain or tincture appears in some cases to have affected the internal ends
of the cells which line the follicles or ultimate saccules of the liver. This color is able to survive
prolonged immersion in chromic acid and alcohol, and does not allow carmine to replace it in
sections which have been stained with an ammoniacal solution of that color, the effect of which
is to produce a result similar to double staining in green and red. The singular green ele-
ments scattered through the connective tissue remain equally well defined, and do not take the
carmine dye. I at first believed these to be parasitic vegetable organisms, and I also sup-
posed I saw starch granules in them, which physical tests with an iodine solution failed to con-
firm. These large and small green granular bodies in the connective tissue, and those close to
the intestinal wall, as well as those in the heart I, find present in fewer numbers in white-fleshed
Oysters, but simply with this difference, that they are devoid of the green color. It is evident,
therefore, that they cannot be of the nature of parasites, though the color is limited to them,
only the surrounding tissue, except in the region of the heart, appearing of the normal tint.
This condition of the specimens observed by me does not, however, disprove the possibility of
the occurrence of vegetable parasites in the Oyster, where there is as much, or perhaps more
likelihood of their occurring than in some much more highly organized animals.
It is a fact, however, that the Oyster is singularly free from true parasites of all kinds; the
COLORS OF DIFFERENT PARTS OF THE OYSTER. 741
oyster-crab being perhaps the only creature which is ever frequently found within its valves,
and then only as a harmless messmate. More recently it has been my good fortune to be able to
study a second lot of European Oysters, in two varieties of which the green color was unusually
developed, especially in the heart. In a specimen of Falmouth Oyster I found a large eyst or
sac in the mantle near the edge filled with green cells, which, like those in the heart, when opened
readily separated from one another, being quite as independent of each other as the ordinary
discoidal corpuscles in the serum of red blood. The hearts of affected specimens were found to
have the wall of the ventricle abnormally thick, and covered inside with the readily detachable
green cells in a thick layer and measuring one three-thousandth of an inch in diameter. An appli-
cation of the test for starch with iodine gave a negative result. If iodine was first applied to
these cells in strong solution, and they were then treated with sulphuric acid, the characteristic
blue reaction was not developed, showing that there was no cellulose wall covering them, and
that they were most positively not parasitic, algous vegetable organisms. In potassic hydrate
solution they were completely dissolved, a further proof of the absence of cellulose.
Their dimensions, one three-thousandth of an inch, is the same as that of the blood-cell of the
Oyster. They are nucleated, with the nucleus in an eccentric position as in the blood-cell of the
animal. Their occurrence in the heart and gills so as to tinge those organs of their own color is
almost positive proof of their true origin and character. Furthermore, I find in sections that they
sometimes occlude the blood-channels. In the cysts in the mantle, as in the heart, they are free,
and in the normal untinged heart they are not abundant. All of the foregoing facts indicate that
these green bodies are in reality blood-cells which belong to the animal. How they become green
is not easy to determine. The fact remains that no evidence of the presence of green Micrococei
or Microbia, as independent existences, could be made out. The fact that I found instances in green
Oysters where an unusual greenish material was found in the follicles of the liver, the living cells
of which were also affected, would indicate that the color was probably absorbed from the food of
the animal, which, as we know, consists largely of living vegetable matter. It is not improbable
that the tinged nutritive juices transuded through the walls of the alimentary canal acquired the
color of the food which had been dissolved by the digestive juices.
How to account for the accumulation of the green cells in the heart and in cysts in the
mantle is not, however, an easy matter, unless one be permitted to suppose that the acquisition
of the green color by the blood-cells is in reality a more or less decidedly diseased condition, for
which we have no ground in fact, since the green Oysters are in apparently as good health as the
white ones. They were found ‘fat’ or ‘poor,’ just as it may have happened that their food was
abundant or the reverse. They are also found in all stages of the ‘greened’ condition. Sometimes
they have only a very faint tinge of the gills, or they may be so deeply tinged as to appear
unpalatable, with the heart of a deep green, or with green cysts developed in the mantle, or with
clouds of this color shading the latter organ in certain places. A vastly greater proportion of
green Oysters are eaten in this country, at all events, than is generally supposed, especially of
those just faintly tinged in the gills.
The most important glandular appendage of the alimentary tract of the Oyster is the liver.
Jt communicates by means of a number of wide ducts with a very irregularly formed cavity, which
We may designate as the stomach proper, in which the food of the animal comes into contact with
the digestive juices poured out by the ultimate follicles of the liver, to undergo solution preparatory
‘to its absorption during its passage through the singularly formed intestine.
If thin slices of the animal are examined under the microscope we find the walls of the
stomach continuous with the walls of the great ducts of the liver. These great ducts divide and
742 NATURAL HISTORY OF AQUATIC ANIMALS.
subdivide until they break up into a great number of blind ovoidal sacs, into which the biliary
secretion is poured from the cells of their walls. A thick stratum of these follicles surrounds the
stomach, except at its back or dorsal side. It is not correct to speak of the liver of the Oyster as
we speak of the liver of a higher animal. Its function in the Oyster is the same as that of three
different glands in us, viz, the gastric follicles, the pancreas, and the liver, to which we may add the
salivary, making a total of four in the higher animals which is represented by a single organ in
the Oyster. In fact, experiment has shown that the secretion of the liver of mollusks combines
characters of at least two, if not three, of the glandular appendages of the intestine of vertebrated
animals. There are absolutely no triturating organs in the Oyster for the comminution of its
food; it is simply macerated in the glandular secretion of the liver and swept along through the
intestine by the combined vibratory action of innumerable fine filaments with which the walls of
the stomach, hepatic ducts, and intestine are clothed.
In this way the nutritive matters of the food are acted upon in two ways: first, a peculiar
organic ferment derived from the liver reduces them to a condition in which they may be absorbed;
secondly, in order that the latter process may be favored it is propelled through an intestinal
canal which is peculiarly constructed so as to present as large an amount of absorbent surface as
possible. This is accomplished by a double induplication or fold which extends for the whole
length of the intestine, the cavity of which in consequence appears almost crescent-shaped when
cut straight across. On the concave side the intestinal wall is thrown into numerous very narrow
longitudinal folds, which further serve to increase the absorbing surface. Such minor folds are
also noticed in the stomach, and some of these may even have a special glandular function. There
are no muscular fibers in the wall of the intestine as in vertebrates, and the sole motive force
which propels the indigestible as well as digestible portions of the food through the alimentary
canal is exerted by the innumerable vibratory cilia with which its inner surface is clothed. The
intestinal wall is wholly made up of columnar cells which are in direct contact externally with
the connective tissue which is traversed by numerous large and small bloodvessels devoid of
specialized walls.
This apparatus is admirably suited to render the microscopic life found in the vicinity of the
animal available as a food supply. The vortices created. by the innumerable vibratory filaments
which cover the mantle, gills, and palps of the Oyster enables it to draw its food toward itself,
and at the same time the microscopic host is hurled into the capacious throat of the animal to
undergo conversion into its substance as described above. The mode in which the tissues may
become tinged by the consumption of green spores, diatoms, or desmids it is easy to infer from
the foregoing description of the digestive apparatus of the animal; and the colorless blood-cells,
moving in a thin, watery liquor sanguinis, would, judging from their ameebiform character, readily
absorb any tinge acquired by the latter from the intestinal juices.
217. LOCAL VARIATIONS IN THE FORM AND HABITS OF THE OYSTER.
Mr. Darwin (‘Variation of Animals and Plants,” vol. ii, 2d ed., p. 270) writes: “With
respect to the common Oyster, Mr. F. Buckland informs me that he ean generally distinguish the
shells from different districts; young Oysters brought from Wales and laid down in beds where
‘natives’ are indigenous, in the short space of two months begin to assume the ‘native’ character.
M. Costa’ has recorded a much more remarkable case of the same nature, namely, that young
;
' Bull. de la Soc. Imp. d’Acclimat., viii, p. 351.
EFFECT OF HEAT UPON OYSTERS. 743
shells taken from the shores of England and placed in the Mediterranean at once altered their
manner of growth and formed prominent diverging rays, like those on the shells of the proper
Mediterranean Oyster. The same individual shell, showing both forms of growth, was exhibited
before a society in Paris.”
VARIATIONS IN THE SHELL.—The statement by Mr. Buckland in regard to the local forms of
Ostrea edulis is undoubtedly true, as I know from personal observation of specimens obtained for
me from various parts of Europe through the efforts of Professor Baird. In some cases the local
differences between the shells from different places were so marked that had a person mixed certain
lots together indiscriminately without my knowledge I could afterwards certainly have sorted out
the more marked varieties. Local influences also very largely determine the ‘“‘ greening” of Oysters,
as I can assert from personal obseryation of both the American and European species. Practical
oystermen affirm that they can readily discriminate the local varieties of Oysters grown in various
noted localities along the eastern coast of the United States. From what I have seen it is very
probable that this may be the case, as one may often observe well-marked differences of form as
well as color.
Local adaptation undoubtedly takes place, for how else are we to account for the fact that
a change in the specific gravity of the water to which the adult has been accustomed will kill the
milt? This point has an important practical bearing in relation to the effect of heavy rains in
diluting the water when the animals are spawning. Might not a marked change in the specific
gravity of the water at the time of spawning kill all the spermatozoa which are set free, and thus
also prevent the impregnation of whatever mature ova were being thrown out at that time by
the adults?
INFLUENCE OF TEMPERATURE.—Certain it is that temperature has an influence upon the
time of spawning. A lot of Oysters marked “ Anglo-Portuguese,” which had been transplanted
from Portuguese to English waters, and which I received in the month of March and others
in January last, had the reproductive organs remarkably advanced in development as compared
with specimens of O. edulis from different parts of England, Wales, Scotland, Holland, and France.
So great was this difference that, although planted for some time in the colder waters of England,
the reproductive organs of the Portuguese form had not apparently had their disposition to
become functionally active at this early season influenced to any great extent. In fact, I obtained
living mature eggs and milt from a number of specimens of this variety, while I looked in vain
for ripe spawn in any of the others of the true O. edulis. This would indicate that the influence of
temperature, though not altogether hereditary in this case, was persistent, and had so impressed
itself that the reproductive organs of these Oysters, coming from a warmer latitude, had begun
to mature their sexual products even after transplanting into more northerly and colder waters
much sooner than the natives of those same latitudes.
Like this persistent influence of a climate to which certain forms of Oysters have been long
accustomed, the influence of the specific gravity of the water of a certain locality may also be
persistent. The Oysters of Saint Jerome’s Creek seem to be adapted to the specific gravity of
the water of the vicinity, so that if artificial sea-water is prepared, differing much in this regard
from the native water, we find that the spermatozoa are immediately killed if put into it. From
this it follows that if the specific gravity to which the adults become accustomed is normal to
their sexual products, may it not be well to look into the effect of such changes upon the health
of the adults ?
I have met with spawning Oysters in December, such at least in which the spawn was nearly
Mature, but this was an exceptional case. I find them in April and May in considerabie abun-
744 NATURAL HISTORY OF AQUATIC ANIMALS.
dance; the months of May, June, and July may, however, be regarded as their principal spawning
months. Ripe spawn may be sparingly obtained in the latter part of August, and even up to
the first of October, but the three months mentioned are the periods during which the experi-
mentalist ought to be in the field prepared for work in this, the latitude of Washington. What
amount of variation from this period may be made manifest as we go north or south along the
eastern coast of the United States I am unable to state; and what amount of local variation may
also be due to causes of a purely local character I am also unable to say, not having examined
the Oysters at a sufficient number of localities to make such facts as I may possess of any
value.
218. THE OYSTER-CRAB AS A MESSMATE AND PURVEYOR.
It is many years since Mr. Say named the little Oyster-erab Pinnotheres ostreum, and its habits
since that time seem to have excited but little interest. Professor Verrill, in his observations pub-
lished in the “Report of the United States Fish Commissioner for 187172,” records the fact that
it is the female which lives in the Oyster, and that the male, which is smaller and unlike the
female, especially in the form of the abdominal segments of the body, is rarely if ever seen to
occur as a messmate of the Oyster, but that he has seen it swimming at the surface of the water
in the middle of Vineyard Sound. He also says that they occur wherever Oysters are found.
This singular little crab has quite a number of allies which inhabit various living mollusks, holo-
thurians, ete., of which admirable accounts are given by Van Beneden in his work on “ Animal
Parasites and Messmates,” and also by Semper in his treatise entitled ‘‘ Animal Life.”
QUADRUPLE COMMENSALISM.—The Oyster-crab is a true messmate, and it is in the highest
degree probable that the presence of these animals in the mantle cavity of the Oyster is to be
regarded as advantageous rather than otherwise. The animal usually lives between the ventral
lobes of the mantle of its host, into which the four lobes of the gills and palps also depend,
and, as will be seen from the following observations, may be the means of indirectly supplying
its passive protector with a portion of food. During a trip down the Chesapeake in July, 1880,
while I was with the Fish Commission vessel, some Oysters were dredged up by the crew which
contained some Oyster-crabs. In the case I am about to describe the included crab was a female
with the curiously expanded, bowl-like abdomen folded forward under the thorax, partially
covering a huge mass of brownish eggs. Upon examining these eggs, what was my astonish-
ment to find that they afforded attachment to a great number of compound colonies of the
singular bell animaleule, Zodthamnium arbusculum. Upon further examination it was found that
the legs and back of the animal also afforded points of attachment for similar colonies, and
that here and there, where some of the individuals of a colony of Zodéthamnium had been sepa-
rated from their stalks, numerous rod-like vibriones had affixed themselves by one end. In this
way it happens that there is a quadruple commensalism established, since we have the vibriones
fixed and probably nourished from the stalks of the bell animalecule, while the latter is benefited
by the stream of water drawn in by the cilia of the Oyster, and the last feeds itself and its protegé,
the crab, from the same food-laden current. Possibly the crab inside the shell of its host catches
and swallows food which in its entire state could not be taken by the Oyster, but in any event
the small crumbs which would fall from the mouth and claws of the crab would be carried to
the mouth of the Oyster, so that nothing would be wasted.
We must consider the crab with its forest of bell animaleules in still another light. Sinee
the animateules ave well fed in their strange position, it is but natural to suppose that they would
DEVELOPMENT OF THE OYSTER-CRAB. 745
propagate rapidly, and that the branches of the curious tree-like colonies would also inerease in
numbers. The individuals of the colonies multiply in about three ways: first, by branching ;
secondly, by splitting lengthwise; thirdly, certain much enlarged and overfed zodids divide cross-
wise. By the two last modes one-half of the product is often set free, the free animaleules
So originated being known as “swarmers.” These cast-off or free zodids which drop from the
colonies are no doubt carried along by the vortex created by the cilia of the gill and palps, and
hurled into the mouth and swallowed as part of the daily allowance of the food of the Oyster.
We mnay therefore regard Pinnotheres, in such instances, as a veritable nursery, upon the body and
legs of which animalcules are continually propagated and set free as part of the food supply of
the Oyster, acting as host to the crab. I do not suppose, however, that such a condition will
always be found to obtain, and it must also be remembered that myriads of Zodthamnium colonies
were dredged up attached to the fronds of the handsome Grinnelia, a red alga commonly found
in certain parts of Chesapeake Bay. Where this plant grows in abundance on the bottom I have
estimated that one might find upwards of a hundred animalcules attached to a square inch of
frond surface, which would indicate an animalcular population of upwards of four millions of
individuals to the square rod, a number as great as that of the human inhabitants of the city of
London.
DEVELOPMENT OF THE OYSTER-CRAB.—The Oyster-crab undergoes a development and
metamorphosis similar to that of our edible crab, Callinectes, but the body in the Zowa stage
is blotched with dark, branched pigment cells. The eyes also are vastly more developed than
in the adult, where they are partly suppressed from disuse. There is no dorsal spine, nor are
the antennary and rostral appendages so well developed as in the Zova of Callinectes. Arter the
young are hatched they probably leave the abdominal covering of the parent, swim out of the
Oyster for a season, and, if female, seek a permanent abode in some Vyster near by, behaving
somewhat like the species described by Semper as inhabiting the water-lungs of certain holothu-
rians. After undergoing further development, the young Pinnotheres reaches the megalops stage
of its development, when it is probable that the choice of its home takes place. After it has
entered the mantle cavity of its host as a diminutive larva, and has grown to be adult, when
it measures a half inch or more in diameter, it is probably ever after a prisoner within the
shell of its molluscan protector. It undergoes a retrogressive metamorphosis as it grows adult,
its eyes become relatively less conspicuous than in youth, and it never has a thick, hard shell
like its allies which live in the open water, but the external skeleton remains almost entirely soft
and chitinous, or in the state in which we commonly find the outer covering of an edible crab
which has just molted. This arises apparently from the conditions by which the animal is sur-
rounded; the protection afforded it by its host does away with the need of a thick, hard covering
such as we find inclosing the bodies of its free-swimming allies. Unlike the latter, too, the limbs
of the Oyster-crab are to some extent degenerate and weakened; its chele or claws are feeble,
and, when removed from its home, seems a very sluggish, helpless sort of creature, without a
particle of the pugnacity of its allies, and if placed on its back will sometimes remain in that
position helplessly beating the air with its weak limbs. This is a remarkable instance, which also
serves very admirably to illustrate the principle of degeneration in organic evolution, so ably
dealt with by Prof. E. Ray Lankester.
The Oyster itself is also an example of.the effect of disuse in producing retrograde develop-
ment, and even shows signs of gradual adaptation when removed from one locality to another.
Unlike most other bivalves, the Oyster has no soft muscular foot which it may protrude outward
from between the edges of its valves. No visible rudiment of such a prominence can be found
146 NATURAL HISTORY OF AQUATIC ANIMALS.
in the adult, though something of the sort, it is asserted by embryologists, appears to be devel-
oped in the larve. As the Oyster lost its power of locomotion from the non-development of
the foot, due doubtless to a gradually acquired sedentary habit which has become permanent.
the pedal structures have been almost entirely aborted, leaving nothing excepting the poorly
developed pedal muscles described by Dall. There is accordingly little or no evidence of the
existence of a pedal or foot ganglion in the Oyster, because there is no need for one, as in other
forms; it, too, has disappeared with the structure which required its presence.
Returning to the consideration of the Oyster-crab, it is well known that it is much relished
by many persons. The animal may be eaten alive, and has a peculiar, agreeable sweetish taste.
Recently an enterprising New York party has taken to canning them, the supplies for this purpose
being obtained from some of the large oyster-canning establishments. The economic value of the
animal as food, although not great, is sufficiently important to demand a passing notice.
219. PHYSICAL AND VITAL AGENCIES DESTRUCTIVE TO OYSTERS.
Most of the observations which follow were made at Saint Jerome’s Creek, Maryland, but
inasmuch as the physical and vital enemies of Oysters appear to be similar the world over, I have
no hesitation in reproducing what [ have previously published elsewhere. And of physically
injurious agents the black ooze or mud found in the vicinity or on the bottom of many of our
most valuable beds and planting grounds is probably the most to be dreaded if it accumulates
in too great quantity.
The origin of the black ooze at the bottom ean be traced directly to the sediment held in
suspension in the water which slowly ebbs and flows in and out of the inclosure, carrying with it
in its going and coming a great deal of light organic and inorganic débris, the former part of which
is mainly derived from the comminuted fragments of plants growing in the creek. This seemed to
be the true history indicated by what was noticed in studying the box-collector. The same opinion
is held as to the origin of this mud by both Coste and Fraiche in their works on oyster-culture.
There is probably no worse enemy of the oyster-culturist than this very mud or sediment.
It accumulates on the bottom of the oyster-grounds, where in course of time it may become deep
enough to cause serious trouble. Especially is this true of ponds from which the sea ebbs, and to
which it flows through a narrow channel. The falling leaves from neighboring trees in autumn
also contribute to this pollution, as well as heavy rains which wash deleterious materials into it.
Adult Oysters which are immersed in part in this mud struggle hard to shut it out from
their shells. If one will notice the inside of the shells of Oysters which have grown in a muddy
bottom, it will often be seen that there are blister-like cavities around the edges of the valves
filled with mud, or a black material of a similar character. There is not the slightest doubt
in my mind that in these cases the animal, in order to keep out the intruding mud, has had
recourse to the only available means at its command. A great many of the Oysters in the pond
are affected in this manner, but it is extremely uncommon to find shells of this kind in opening
Oysters coming from a hard bottom. It is easy to understand that such efforts at keeping out
the mud from the shell will not only waste the life forces of the animal, but also tend to greatly
interfere with its growth. The importance, therefore, of artificial preparation is apparent, where
it is desirable to establish ponds for the successful culture of this mollusk.
Only in one case have I observed that the mud tended to impair the flavor and color of
the Oyster. In this instance the animal was thoroughly saturated with the black ooze, the very
tissues seeming to be impregnated with the color, the stomach and intestine loaded to engorge-
ment with the mud, the animal manifesting every sign of being in a decidedly sickened condition.
EFFECT OF SEDIMENT UPON YOUNG OYSTERS. 747
The cause of this was probably that the shell with its tenant had sunken too deeply into the
mud when the ingestion of the black ooze commenced, giving rise to the remarkable changes
which I have recorded. No doubt had this condition of things persisted for long the animal
would have been smothered by the mud.
MUD AND THE YOUNG FRY.—The accumulation of the slightest quantity of sediment around
a young Oyster would tend to impede its respiration, and in that way destroy it, yet in the natural
beds there are so few naturally clean places which remain so that it is really surprising that so
many young Oysters pass safely through the critical periods of their lives without suceumbing to
the smothering effects of mud and sediment. When it is borne in mind that at the time the infant
Oyster settles down and fixes itself once and for all time to one place, from which it has no power
to move itself, it measures at the utmost one-eightieth of an inch, it will not be hard to under-
stand how easily the little creature can be smothered even by a very small pinch of dirt. The
animal, small as it is, must already begin to breathe just in the same way as its parents did before
it. Like them its gills soon grow as little filaments covered with cilia, which cause a tiny current
of water to pass in and out of the shell. The reader’s imagination may be here allowed to esti-
mate the feeble strength of that little current, which is of such vital importance to the tiny Oyster,
and the ease with which it may be stopped by a very slight accumulation of dirt. Mdébius esti-
mates that each Oyster which is born has 77323555 Of a chance to survive and reach adult age. So
numerous and effective are the adverse conditions which surround the millions of eggs matured by
a single female that only the most trifling fraction ever develop, as illustrated by the above caleu-
lation. The egg of the Oyster, being exceedingly small and heavier than water, immediately falls
to the bottom on being set free by the parent. Shauld the bottom be oozy or composed of
sediment its chances of development are meager indeed. Irrecoverably buried, the eggs do not
in all probability have the chance to begin to develop at all. The chances of impregnation are
also reduced, because the male and female Oysters empty their generative products directly into
the surrounding water, whereby the likelihood of the eggs meeting with the male cells becomes
diminished. What with falling into the mud and what with a lessened chance of becoming
impregnated, it is not unlikely that Mébius’ estimate is very nearly correct; but the American
Oyster, whose yield of eggs is much greater, not only on account of its larger size, but also
because the eggs are smaller than those of the European, has probably still fewer chances of
survival. The vigorous growth of small organisms on surfaces fitted for the attachment of young
Oysters also tends to cause sediment to gather in such places in the interstices of the little
organic forest, where the eggs of the Oyster no doubt often become entombed or smothered by the
crowded growth surrounding them.
‘‘ In addition to the active, animate enemies of the Oyster, the beds suffer seriously, at certain
times, from the elements. . . . Great storms will sweep the Oysters all off the beds, bury
them under shifting sand or mud, or heap upon them the drifting wrack torn from the shores.
Beds which lie at the months of rivers are liable to be injured by floods also, which keep the
water wholly fresh, or bring down enormous quantities of silt and floating matter, which settles
on the beds and smothers the Oysters.
“A few years ago a large tract of peat was drained at Grangemouth, Scotland. The loose
mud and moss was carried down the drains upon an oyster-bed in the estuary; the consequence
was that the Oysters were covered over with mud and entirely destroyed. Nothing is so fatal to
Oysters as a mud storm, except it be a sand storm. The mud and the sand accumulate in the
Oyster’s delicate breathing organs and suffocate him.
“North of Long Island an enemy is found which does not exist in the milder south, in the
— tt ini
748 NATURAL HISTORY OF AQUATIC ANIMALS.
shape of ‘ground-ice’ or ‘anchor-frost.’ It is little understood, though often experienced, and I
was able to collect only vague data in regard to it. It appears that in hard winters the bottom of
the bays freezes solid in great patches, even at a depth of fifteen or twenty feet. The mud freezes
so hard that rakes cannot be pressed into it; and if a stronger implement, like a ship’s anchor, is
able to penetrate it. the crust comes up in great chunks. These frozen patches are sometimes
forty feet square and continue unthawed for long periods. When such ‘anchor-frost’ takes place
at an Oyster-bed, of course the mollusks are frozen solidly into the mass, and few of them ever
survive the treatment. To the Cape Cod planters this is a serious obstacle to success.”?!
INTERFERENCE OF OTHER ANIMAL LIFE.—We have called attention to the probable inter-
ference of small organic growths to the fixation of the young fry; in practice it is found that the
larger organic growths which establish themselves on the collectors also become injurious. The
two most conspicuous types are the sessile ascidians or tunicates and the barnacles. I have
frequently found fully one-half of the surface of a slate covered with a dense colony of ascidians;
in this condition a great percentage of available surface is lost which ought to serve for the
attachment of spat. The surfaces so occupied would also be comparatively clean were it not for
these organisms, which actually become a serious annoyance. They, like the Oyster, affix
themselves to the slates while still in the free-swimming larval stage, since the surfaces designed
for the Oyster are equally well adapted to them. The barnacles, which also affix themselves in
great numbers, become a nuisance for the same reason. The larval barnacle is an extremely
active little creature, and dashes about in the water with great rapidity. As soon as it has
completed this stage of its growth it betakes itself to some object, to the surface of which it
attaches itself by the head end, when a singular change takes place, at the end of which it is
found that it has begun the construction of the curious conical shell which it inhabits. They
grow very rapidly, so that in a couple of months the shell will already measure over half an inch
in diameter. In this way further inroads are made upon the room which should be taken up by
Oysters. ;
Of course the larger types are not alone in taking up space, since infusorians, bryozoans,
polyps, ete., are also culpable, as well as alge, such as diatoms and the higher forms. ‘The only
remedy for this accumulation of animal growths on the surfaces of the slates and other collecting
apparatus will be to have the frames which hold the slate in position so arranged that each tile,
shingle, or slate can be removed, in order that it may be readily overhauled and these organisms
removed from the surfaces which it is desired shall remain clean. This work would have to be
done at intervals of every two or three weeks, and should be conducted with great care, so as not
to remove the Oysters which have affixed themselves along with the other things which it is the
jntention to destroy. The removal of the smaller forms from the surfaces of the slate would be
more difficult, and attended with danger to the fry already attached. With this object in view,
I would suggest the use of wooden racks or frames lying horizontally, which would receive the
slates into deep notches made with a saw, so as to hold them vertically or edgewise, rendering
their removal, for the purposes of cleansing, and their replacement an easy matter. Other
devices would no doubt answer the same purpose and be more convenient even than the last.
If posts were securely fixed in the bottom eight or ten feet apart, so as to project a foot or so
above the water at the highest tide, a single board six inches wide, nailed against the tops of the
posts edgewise, and extending from one to the other, would provide a simple arrangement from
which to hang the slates singly by means of galvanized wire fastened or hooked to nails partly
driven into the board. By the help of this plan one man with a boat could overhaul many
1. INGERSOLL, Report on Oyster Industry, Tenth Census.
ENEMIES OF THE OYSTERS. 749
hundreds of slates in a single day, and effectually care for them for a whole season. This last
contrivance would not answer well perhaps where there was a swift current, but would be a most
admirable arrangement in still ponds or ‘claires.’. In such places the whole area might be
provided with posts grouped or placed in rows, so that when the attendant was at work he could
pass in order from one row to the other in a narrow boat, or two attendants in one boat could take
care of two rows, the ones on either hand, at the same time.
Star-fishes are notorious for the havoc they are capable of making among Oysters. They
have the power apparently of everting their saccular stomachs and extracting the soft parts of
their prey from the shell. Whole beds have been seriously injured by the inroads of these
creatures. They do not seem to be dreaded much in the Chesapeake Bay, however, and appear
to annoy the oyster-planters of New England most seriously.
“The oyster-catcher, and some other birds, steal not a few at low tide. Barnacles, annelids,
and masses of hydroid growth sometimes form about the shells and intercept the nutriment of the
poor mollusk, until he is nearly or quite starved; this is particularly true in Southern waters. At
Staten Island the planters are always apprehensive of trouble from the colonization of mussels on
their oyster-beds. The mussels, having established themselves, grow rapidly, knit the Oysters
together by their tough threads, making culling very difficult, and take much of the food which
otherwise would help fatten the more valuable shell-fish. In the Delaware Bay the spawn of
squids, in the shape of clusters of egg-cases, appropriately called ‘sea-grapes,’ often grows on the
Oysters so thickly, during the inaction of summer, that when the fall winds come, or the beds are
disturbed by a dredge, great quantities of Oysters rise to the surface, buoyed up by the light
parasitic ‘grapes,’ and are floated away. This is a very curious danger. Lastly, certain crabs
are to be feared—chiefly the Callinectes hastatus, our common ‘soft crab,’ and the Cancer irroratus.
Probably the latter is the more hurtful of the two. I have heard more complaint on this score at
the western end of the Great South Bay, Long Island, than anywhere else. Mr. Edward Udall
told me that the crab was the greatest of all enemies to Oysters on the Oak Island beds. They eat
the small Oysters up to the size of a quarter-dollar, chewing them all to bits. These are on the
the artificial beds, for they do not seem to trouble the natural growth. But tolled by broken
Oysters, when the planter is working, they come in crowds to that point. Mr. Udall stated that
once he put down five hundred bushels of seed brought from Brookhaven, and that it was utterly
destroyed by these crabs within a week and while he was still planting. He could see the crabs,
and they numbered one to every fifty Oysters. It is well known that in Europe the crabs are
very destructive to planted beds, and it is quite possible that many mysterious losses may be
charged to these rapacious and insidious robbers. By the way, Aldrevandus and other of the
naturalists of the Middle Ages entertained a singular notion relative to the crab and the Oyster.
They state that the crab, in order to obtain the animal of the Oyster, without danger to their
own claws, watch their opportunity when the shell is open to advance without noise and cast a
pebble between their shells, to prevent their closing, and then extract the animal in safety.
‘What craft!’ exclaims the credulous author, ‘in animals that are destitute of reason and
voice.’”!
In a specimen of the common Ostrea virginica, recently handed me for examination by my
friend, Mr. John Ford, the substance of the shell was thoroughly cavernated so as to render it
extremely brittle and readily crushed; in fact, the inner table of the shell left standing showed a
great number of elevations within, which indicated points where the intruding parasite had been
kept out by the Oyster, which had deposited new layers of calcareous matter at these places so
1. INGERSOLL: Report on the Oyster Industry, Tenth Census.
750 NATURAL HISTORY JF AQUATIC ANIMALS.
as to give rise to the elevations spoken of. Besides this, the inner table had become so weakened
at the insertion of the adductor muscles that the animal in closing had torn a part of it loose,
which had been repaired by the deposition of a brown, horny substance. Evidence of the presence
of the boring sponge may very frequently be noticed in shells of Oysters brought to the markets,
though it often appears as if the parasite had left its work incomplete, being killed on its host.
I find that Schmidt has also noted this, and that the boring operations of the sponge usually seem
to stop in the case of living mollusks at the nacreous layer.
Upon examining some Scotch Oysters, obtained for me for study by Professor Baird,-I was
struck with the fact that every one was infested with this organism. The effect of the parasitism
was that all of the specimens had abnormally thick shells, due evidently to the effort made by
the Oyster to deposit more and more calcareous matter in order to exclude its persistent tormentor.
Internally the shell showed irregularities due to the intrusion of the sponge. Itis highly probable
that in this case the growth of the Oysters had been impeded by the parasite, in consequence of
the effort made by the animals to exclude their enemy by increasing the thickness of their shells.
This same tendency to increase the thickness of the valves I have noticed in specimens of our
native Oyster, the shells of which were infested with this parasite. It is very remarkable that the
Oyster should make an effort to exclude its enemy by such a means; and it is not less remarkable
to observe that the lime carbonate secreting function of the mantle is often stimulated to extra
exertion long before the parasite has actually intruded into the cavity of the shell.
Dr. Leidy gives a lucid account of the living sponge as found in Ostrea virginiana and Venus
mercenaria. He says: “This boring sponge forms an extensive system of galleries between the
outer and inner layers of the shells, protrudes through the perforations of the latter tubular
processes, from one to two lines long and one-half to three-fourths of a line wide. The tubes are
of two kinds, the most numerous being cylindrical and expanded at the orifice in a corolla form,
with their margin thin, translucent, entire, veined with more opaque lines, and with the throat
bristling with siliceous spicules. The second kind of tubes are comparatively few, about as one is
to thirty of the other, and are shorter, wider, not expanded at the orifice, and the throat unob-
structed with spicule. Some of the second variety of tubes are constituted of a confluent pair,
the throat of which bifurcates at bottom. Both kinds of the tubes are very slightly contractile,
and under irritation may gradually assume the appearance of superficial, wart-like eminences
within the perforations of the shell occupied by the sponge. Water obtains access to the interior
of the latter through the more numerous tubes, and is expelled in quite active currents from the
wider tubes.”
The boring process seems to be effected by the action of the living soft material of the sponge,
according to observations which have recently been made by a Russian naturalist, according to
whom it appears that the calcareous matter is dissolved away by the parasite. I am told by a
practical oysterman that a bed once planted with Oysters which are badly infested by the boring
sponge is apt to remain so for some time, and that the beds adjoining become infested, for the
reason that the embryo sponges, which are thrown off in large numbers from the infested “plants,”
swim about in the water, attach themselves to other Oysters, to begin their injurious growth and
excavations in sound shells.
220. NATURAL AND ARTIFICIAL OYSTER-BANKS.
CHARACTERISTICS OF NATURAL OYSTER-BANKS.—I have examined a number of oyster-
banks, which were readily accessible in shallow water, with gratifying results as to the habits
of the animal under virtually undisturbed conditions. These banks, like those formed by the
POSITIONS OF THE SPAT, 751
European Oyster, always appear to be much longer than wide, but many of them are almost
entirely exposed to the air during low tide, a rare occurrence, according to Mébius, with the
banks on the Schleswig-Holstein coast of the North Sea. I learned from the owners of
some of these banks that, although a considerable proportion of the Oysters on them were
at times frozen to death during the severe winters, the fecundity of those which remained was
such, combined with the naturally favorable conditions found on the banks for the growth
of old and young, as to restore the beds to their wonted productiveness in one or two seasons.
Whether this description of the fecundity of the beds found in shallow water is overdrawn
or not matters little, since there was the plainest evidence that we had here before our eyes
the best natural conditions for the propagation and feeding of the individuals. The beds are,
in a word, natural spat-collecting grounds; places where such conditions obtain as will allow a
large proportion of the swarming brood of the spawning season to affix itself securely and survive
in positions where an abundance of food may be got. The tide ebbing and flowing over the beds
not only carries with it in suspension the microscopic food best adapted for the nourishment of the
Oysters, but alse tends, owing to the peculiar arrangement of the shells on the banks, to keep the
surface of the latter clean, so as to be well adapted as favorable points of attachment for the young.
Tn all of the natural banks which I have had the pleasure of examining in the Chesapeake,
the individual Oysters assume an approximately vertical position.. The assumption of this position
seems perfectly natural; with the hinge end downwards and the free edges of the valves directed
upward the animals are in an excellent position to feed, while the outside vertical surfaces of the
valves are well adapted to afford places of attachment for the spat. The latter, however, appears
to attach itself in the greatest abundance to the old Oysters at the surface of the bank. The result
is that when one removes the Oysters from the bed they are found to adhere together in clusters,
generation after generation being piled one on top of the other in succession. As many as four
generations may be made out in most cases; the oldest being buried in the mud and sand below
and is often found to be smothered by those which have followed. Even below the last stratum
of living Oysters, if one keeps digging, it is discovered that the shells of numerous still more
remote ancestors of the living ones now occupying the bed are disposed vertically in the sand and
earth beneath. Attached to the upper edges of these dead shells follows, we will say, the first
living generation and so on to the fourth, composed mainly of young individuals or spat only a
few days or months old. Whether it is proper to regard the superimposed series of individuals as
generations may be questioned, but as no more expressive word occurs to me, I wish to be under-
stood as using it here with qualifications.
aq POSITIONS OF THE SPAT.—The spat does not fix itself in any constant position; the young
may have the hinge of the shell directed downward, upward, or to the right or left hand.
Singularly enough the shells do not grow in the directions which the free edges of the valves
are made to assume in the young. Should the young happen to be fixed hinge downward
the free edges of the valves grow in length directly upward; in case the hinge is directed
either to the right or to the left, the layers of calcic carbonate will be deposited in
such a way upon one side as to cause the free edges of. the valves to be eventually
directed upwards, causing the umbonal portion of the valves to describe an are of 909.
In case the hinge is at first directed upward, the layers of carbonate of lime will be deposited
_insuch a way by the mantle as to bring the mouth of the shell upward. The attempt to get
“into a vertical position will, however, not always be successful in cases like the last; the are of
“1800, which it is necessary for the animal to traverse from its starting point in order to build
its shell with the free edges opening upward, seem to be a feat a little too difficult of accom-
plishment, in spite of the wonderful persistence of effort manifested by the inhabitant.
752 NATURAL HISTORY OF AQUATIC ANIMALS.
The habit of growing in the erect position, where the banks are prolific and undisturbed.
causes the individuals to be very much crowded together, so that they do not have a chance to
expand and grow into their normal shape. From this cause. overcrowding, the shells of the
individual Oysters become very narrow and greatly elongated; the peculiar forms which result
are known to oystermen as “ Raccoon Oysters,” or ‘‘Cat’s-tongues,” the latter name being probably
derived from a suggestive resemblance to the tongue of a cat. Fossil Oysters appear to have had
the same habit. In some banks their crowded condition may be inferred from the fact that I
counted as many as forty Oysters in an area included by a quadrangle of wire including exactly
one square foot; thirty individuals to the square foot was a fair average on one bank
examined.
All of the observant writers upon the Oyster agree that it is essential that the bottom upon
which oyster-banks are to be permanent should not be liable to shift or be covered by mud or
sediment. The experience of the writer strongly enforces such a conclusion. The permanent
banks, owing to the great number of dead shells scattered through the bottom soil upon which
they have been established, acquire a peculiar solidity or fixedness which the currents of tide water
cannot sensibly affect. When these banks are once covered by the clusters of Oysters more or
less securely held together by the lower portions becoming imbedded in the soil below, and
mutually wedged and fitted together by the any msurfaces of contiguous clusters which have
become neatly adapted to each other by pressure, it is a very hard matter for the tides to smother
the bank unless sufficient soil in suspension is carried by the waters to completely cover the
animals.
ESTABLISHMENT OF ARTIFICIAL BEDS.—The inferences to be drawn from the foregoing
observations are very important. They naturally lead to the inquiry whether artificial Oyster-
beds cannot at least be established in shallow water, where the difficulties in altering the
character of the bottom so as to adapt it to the wants of the Oyster are not practically
insurmountable. I believe that the establishment of artificial beds, which would in time become
similar in every respect to. the natural ones, is possible in a moderately rapid tideway. The
localities, I apprehend, are abundant along the shores of the Chesapeake, and I certainly
know of few places where the existing natural conditions for such a project are any better
than those found in Saint Jerome’s Creek. The bottom would, of course, have to undergo such
preparation as would insure to it solidity, and it might be well to imitate the flat, ridge-like
character of the natural banks in constructing artificial ones. The long axis of the beds should
probably lie transversely to the direction in which the tide ebbs and flows in and out of the
creeks, aS appears to be the case with many banks examined. The next thing to do would be
to colonize these artificial banks with Oysters stuck thickly into the bottom, hinge downward,
imitating the position of the animals in the natural banks. The cost of such an experimental
bank would be comparatively insignificant.
Since the publication of the substance of the foregoing suggestion I have seen the idea
practically realized in the Cherrystone River, Virginia. A heap of Oyster-shells had been
scattered so as to form a low, solid elevation, which was submerged twice a day by the tide.
Upon tnis spat had caught and grown until the whole in two years was as completely and
solidly covered by living natural-growth Oysters as any good natural bank. The desirability
of using the poorly grown stock from natural and artificial banks as ‘seed” for planting
appears reasonable, and could no doubt be made profitable where banks of a sufficient extent
could be established, from which a supply of seed could be obtained.
SPAT-COLLECTORS. 753
I have been informed by an old oysterman that pine bushes stuck securely into the sea
bottom so as to be submerged in shallow areas have been found very effectual as collectors.
In fact, he told me that in one case which had fallen under his observation an oyster-planter
who followed this plan had the satisfaction of seeing his submerged bushes load with spat,
much of which afterwards grew to marketable size. Afterwards a productive ridge or bank
was the result where the brush palisade had originally acted as a collector. Thick palisades
of brush might be stuck into the bottom near permanent oyster-banks with good results.
Doubtless it would be possible to establish banks by this method if, in addition, oyster-shells
or stones were strewn on the bottom along either side of the brush palisade, in order to afford
a foundation for the fixation of the first generations of oysters.
SPAT-COLLECTORS.—Lieutenant Winslow, in 1879, used hurdles or nests of half-round tiles,
eight to sixteen in number; the results from one placed in the Big Annemessex were very flatter-
ing. After it had been immersed twenty-four days 1,506 Oysters had attached themselves. After
forty-five days had elapsed 1,334 still remained, and after ninety-three days were past the number
still adherent was 539. I have had no such success, but in other parts of the bay, as at Tangier
Sound for instance, spat falls in great abundance. I have seen the inner face of one valve of a dead
Oyster furnish attachment for over forty spat from one-eighth to three eighths of an inch in
diameter. Sponges, pieces of wreck, old shoes, pebbles, iron ore, leather, the external surface of
the shell of Modiolaria, branches of trees and logs which have fallen into the water act as collectors.
Oysters are sometimes found inside of bottles which have been thrown upon the bottom, the fry
having wandered through the neck and attached itself to the inner surface, growing to the size of
two inches in diameter and over. The spat is shaped much like the scallop or Pecten, a form which
it often retains until it measures more than two inches in diameter. The primary requisite in
collectors is that they shall present clean surfaces while the spawning season is in progress.
Small inequalities are probably an advantage, as the very youngest spat is often found in chinks
and angles on the shells of the adults. No other organisms should be allowed to grow and cover
up or smother the oyster spat. Barnacles, infusoria, moss animals, polyps, and many other
organisms are liable to accumulate on the surface of the collectors to the detriment of the young
Oysters which have established themselves. Many of these animals, polyps especially, eat the
young fry in the free-swimming stage, as shown by Dr. Horst.
The use of the methods employed abroad for collecting spat has not been tested in the United
States upon a scale large enough to enable us to arrive as yet at any very important conclusions.
Roofing slate coated with mortar promises good results; the valves of oyster shells strung upon
wire, pine cones, and brush have been used, but in unfavorable places, so as to vitiate to some
extent the results which were expected. Fxoy \
Z
SVN SS by
SS = Sx
———— Z gy
a
Fig. 1. The Quahaug or Little-necked Clam, Venus mercenaria. V1G. 3. The Gaper Clam of the West Coast, Schizoth arus nut-
Natural size. talli (Conrad).
Fig. 2. The Quahaug of Puget Sound, Saridomus nuttalli. (1.) Specimen of ordinary size, reduced about one-fourth in length.
Natural size of lar; pecimen. Drawn by-J. H. Emerton phe eiplions ie somewhat contracted; the foot (I?) expands
(II.) Outline of the left valve of a larger specimen, reduced to the
same extent. Drawn from nature by R. I. C, Stearns.
PLATE 257.
=
=== SS
ee
SS =
aS ———
— SO, i = |
Sx SN
SN
————
SSS —_
aS =
ray rT Uy
i) Wee
Z
h
i ?
sare
TH
/ ,
Y Whi) i
i; - ° Mi
|
ey
4 i if Y
/ i. / (
/
ie i
1 Hy) :
LY;
Yy y de y ep
\ \ Ss = =
A / — —
1 C4 JIM TOY TAL
CTT TT
\ VY I 7 OY fit
\ ( al kth ‘)
h / | VA yi
AY AN MAN NY
\\ i Wye
HE PACIFIC.
ey;
vo =
an! _ ——
7 a Coy - vy - :
7 ‘ 7
<
i : - , —_ _— a -
» = aes 4 he Sap re ; Ee ye Ui Aan
5 or : > 7 _ -
PLATE 258.
Fig. 6.
MUSSELS AND SEA CLAMS.
Fic. 1. The Beach Clam or Hen Clam, Spisula soli- Fic. 3. The Mussel, Mylilus edulis, p. 709.
dissima, p. 708. Natural size. Vig. 4. The Black Horse Mussel, Modiola nigra.
1G. 5. The Rough Mussel, Vodiola plicatula, p. 709.
Fig. 2. The Sea Clam, Cyprina islandica. Natural
size. Fic. 6. The Horse Mussel, Modiola modiolus, p. 709.
%
a.
‘ear one
; Aad aft re ¢ Wik: ag Oa a> slbany’|
% »» ; ve e? “an
»y "a een f
? x .¢ ro 7 aay re n giilcisl een ; ; :
ine Wee ii mt i Tian roi maam Ahilias VU nian YH VARA ene ema ‘
; 7 ‘ 1a Mt a Meds) 3 ye t a ‘ =
one ‘ ' Ti. hat heay A yal as ap Tes § Bayi Gio. GAN: me
Lae airn
he eis Ko
Pea nen) 2 6.9).
EXPLANATION OF Fig. 1.
A. Hinge or anterior umbonal end of the left valve of an adult oyster, upon which the soft parts of the animal are represented as they lie
in situ, but with the greater part of the mantle of the right side removed.
au. The auricle of the right side of the heart contracted.
B. Posterior or ventral end of the left valve, which in lite is usually directed upward more or less, and during the act of feeding and respira-
tion is separated slightly from the margin of its fellow of the opposite side to admit the water needful for respiration, and which
also contains the animal's food in suspension.
Bm. Body-mass, traversed superficially by the generative ducts ge.
bj. The organ of Bojanus, or ‘renal’ organ, of the right side of the oyster. (The ducts which it sends into the mantle are not shown, nor
is its connection with the genito-urinary sinus s indicated.)
bp. The large branchial pores which open from the subdivided cavities of the pouch-like gills g into the cloaca el.
br. The anterior branchiocardiac ‘* vein,’ which conveys part of the blood from the gills to the auricle.
c. Right pericardiac membrane, which has been thrown back over M in order co expose the heart ve and au.
cel. Cloacal space, through which the water used in respiration passes out, and into which the excrement of the animal is discharged from the
veut ».
d. Nervous commissure of the right side, which connects the parieto-splanchnic with the supra-csophageal ganglion.
y. Gills, which extend as four flattened transversely subdivided sacs from the palps p to the pointy, at the edge of the mantle.
ge. Superficial network of the generative ducts as they appear when the oyster is spawning.
h. Groove in the hinge end of the lett valve, which receives the ridge developed in the corresponding situation on the right one.
j- Dark brown elastic body or ligament by which the valves are held together at the hinge.
M. Great adductor muscle, which is here viewed from the end, and which is attached to the inner faces of the valves over the dark purple
scars. Itopposesthe elastic ligament and closes the valves, and corresponds to the posterior adductor muscle of dimyary mollusks.
m. Mouth.
mt. Mantle of the left side fringed with two rows of tentacles.
ml’. Portion of the mantle of the right side.
n to z marks the extent to which the right and left leaves of the mantle are joined together; the hood thus formed above and at the sides ef
the palps is called the eueullus.
P. Palps exposed, a part of the cucullus on the right being eut away.
pd. Pedal muscle of right side, which is also inserted upon the shell of the same side,
pg. Parieto-splanchnie ganglion.
s. Genital opening of the right side.
sg. Supra-cesophageal ganglion.
». Vent or anus.
ve. Ventricle of the heart, which is dilated, or in the condition of diastole.
axe. Areas at the edge of the inner surface of the shell, where intruded mud has been inclosed by a thin lamina of shelly matter deposited
by the mantle. ’
y. Point at the posterior extremity of the gills, where the right and left leaves of the mantle are joined together by the membrane which
supports the gills,
EXPLANATION OF FIG. 2.
This figure was drawn from a dissection of a hardened specimen which had been removed from the shell, and is viewed from the left
side, the superficial tissues of the left half of the body-mass having been removed in order to display the surface of the ‘liver’ L, with its
large clusters of minute follicles, and part of the course of the intestine t. Atj the widened pyloric part of the intestine is shown, which
invloses the crystalline style. The ventricle ve and auricle are much contracted, and a spacious pericardiac space is shown on either sideof it.
ge. Stratum of reproductive follicles. The remaining letters of reference are the same as in Fig. 1.
EXPLANATION OF Fi4. 8.
This figure of the viscera of the oyster is also drawn in part from the hardened soft parts, but is viewed from theright side. The great,
ducts d of the ‘liver’ L are shown cut open longitudinally, and are represented as opening directly into the cavity of the stomach st, in front
of which the cesophagus oe is also shown running back from the mouth m. This figure shows almost the entire intestine, with its widened
anterior end j, and its course and curyature as here represented is what will be found constant, even when hundreds of specimens are
examined. Nearly all the substance of the body-mass has been carefully removed from the right half of the body; and where the edges of the
body have been cut through, the stratum of reproductive tissue ge is also shown. The corrugated outer surface of the inner or lower palp
at P. The remaining letters have the same significance as in the previous figures.
EXPLANATION OF FIG. 4.
This represents a section or slice cut from the soft parts of an oyster at the level of the dotted line o in Fig. 3, and viewed from its ante-
rior surface. The tissues and structures, which have been cut across in this section, are as follows:
a’. The dorsal or posterior branch of the great splanchnic artery.
a, The anterior or veutral branch of the splanchnic artery.
br. Branchial vessels.
c. The connective tissue which envelops the organs contained in the body-mass and forms the principal portion of the substance of the
animal in winter.
g. The gills cut across, showing their hollow interiors.
ge. Stratum of reproductive follicles, which immediately underlies the mantle layer mt. Intestinal canal cut through at two points, ii, pos-
teriorly and anteriorly, showing the manner in which the intestinal walls are folded inwards upon themselves.
LL. Right and left lobes of the liver, embedded in the connective tissue and most considerably developed at the sides and below the stomach.
sb. Suprabranchial space.
st. Stomach, showing its irregular form and connection by means of spacious ducts with the “liver.”
ve, Vena cava.
For explanation of figures see
opposite page,
PLATE 259.
LIBRARY OF CONGRESS
LN