Synonym: _Pachymyxa hystrix_ Gruber.
Marine rhizopods, globular or irregular in form, and slow to change
shape. Dimorphic. Both forms multinucleate during vegetative life.
Pseudopodia are long, thin, and thread-form, with rounded ends.
Their function is neither food-getting nor locomotion, but probably
tasting. The plasm of both forms is inclosed in a soft gelatinous
membrane. In one form the jelly is impregnated with needles of
magnesium carbonate (Schaudinn), but these are absent in the other
form. The membrane is perforated by clearly defined and permanent
holes for the exit of the pseudopodia. Reproduction occurs by
division, by budding or by fragmentation, but the parts are
invariably multinucleate. At the end of vegetative life the
needle-bearing form fragments into numerous mononucleate parts; these
develop into adults similar to the parent, but without the spines.
At the end of its vegetative life this new individual fragments into
biflagellated swarm-spores which may conjugate, reproducing the form
with needles. Size up to 2 mm.
Trichosphærium sieboldi Schneider. Fig. 3.
With the characters of the genus. A form which I have taken to be a
young stage of this interesting rhizopod is described as follows:
A minute, almost quiescent, form which changes its contour very
slowly. The membrane is cap-like and extends over the dome-shaped
body, fitting the latter closely. The endoplasm is granular and
contains foreign food-bodies. Nucleus single, spherical, and
centrally located. Pseudopodia short and finger-form, emerging from
the edge of the mantle-opening and swaying slowly from side to side
or quiescent. The most characteristic feature is the presence of a
broad, creeping sole, membranous in nature and hyaline in appearance.
This membrane is the only evidence of ectoplasm, and it frequently
shows folds and wrinkles, while its contour slowly changes with
movements of body. The pseudopodia emerge from the body between this
membrane and the shell margin. Contractile vacuole absent. Length
42µ, width 35µ. In decomposing seaweeds, etc.
Only one specimen of this interesting form was seen, and I hesitate
somewhat in placing it on such a meager basis. It is so peculiar,
however, that attention should be called to it in the hope of getting
further light upon its structure and mode of life. Its membranous
disk recalls the genus _Plakopus_; its mononucleate condition, its
membranous disk, and the short, sometimes branched, pseudopodia
make it difficult to identify with any phase in the life-history of
_Trichosphærium_. I shall leave it here provisionally, with the hope
that it may be found more abundantly another time.
[Illustration: Fig. 3.--_Trichosphærium sieboldi_]
Genus GROMIA Dujardin '35.
(Dujardin 1835; M. Schultze '62; F. E. Schultze '74; Leidy '77;
Bütschli '83; Gruber '84.)
The form is ovoid or globular, and the body is covered by a tightly
fitting, plastic, chitin shell, which, in turn, is covered by a fine
layer of protoplasm. The flexibility of the shell makes the form
variable as in the amoeboid types. The thickness of the shell is
quite variable. The pseudopodial opening is single and terminal. The
pseudopodia are very fine, reticulate, granular, and sharply pointed,
and form a loose network outside of the shell opening. Nucleus single
or multiple. Contractile vacuole is usually absent. Fresh and salt
water.
Gromia lagenoides Gruber '84. Fig. 4.
This species is not uncommon about Woods Hole, where it is found upon
the branches of various types of algæ. The body is pyriform, with the
shell opening at the larger end. The chitinous shell is hyaline and
plastic to a slight extent, so that the body is capable of some
change in shape. The shell is thin and turned inwards at the
mouth-opening, forming a tube (seen in optical section in fig. 4)
through which the protoplasm passes to the outside. The walls of this
tube are thicker than the rest of the shell, and in optical section
the effect is that of two hyaline bars extending into the body
protoplasm. A thin layer of protoplasm surrounds the shell and
fine, branching, pseudopodia are given off in every direction. The
protoplasm becomes massed outside of the mouth-opening and from here
a dense network of pseudopodia forms a trap for diatoms and smaller
Protozoa. The nucleus is spherical and contains one or two large
karyosomes. The protoplasm is densely and evenly granular, without
regional differentiation. I have never observed an external layer of
foreign particles, such as Gruber described in the original species.
Length of shell 245µ; largest diameter 125µ.
[Illustration: Fig. 4.--_Gromia lagenoides_.]
Genus TRUNCATULINA D'Orbigny.
A group of extremely variable foraminifera in which the shell is
rotaline; i. e., involute on the lower side and revolute on the upper
(Brady). The shell is calcareous and coarsely porous in older forms.
The characters are very inconstant, and Brady gives up the attempt to
distinguish the group by precise and constant characters.
Truncatulina lobatula Walker & Jacob.
Synonyms: See Brady '84 for a long list.
"It is impossible to define by any precise characters the
morphological range of the present species. Its variations are
infinite." (Brady, p. 660.)
This very common form, which occurs in all latitudes, was found
frequently among the algæ at Woods Hole. Its characters are so
difficult to define that for the present I shall limit my record to
this brief notice. Size of shell 230µ by 270µ.
Genus ACTINOPHRYS Ehr.
The body is spherical and differentiated into granular endoplasm and
vacuolated ectoplasm, but the zones are not definitely separated.
There is one central nucleus and usually one contractile vacuole. The
pseudopodia have axial filaments that can be traced to the periphery
of the nucleus. Fresh and salt water.
Actinophrys sol Ehr., variety. Fig. 5.
Synonyms: See Schaudinn '95.
The diameter is about 50µ; the vacuolated ectoplasm passes gradually
into the granular endoplasm. This is the characterization given _A.
sol_ by Schaudinn, and it applies perfectly to the freshwater forms.
If I am correct, however, in placing an _Actinophrys_-like form
found at Woods Hole in this species, the description will have to
be somewhat modified. In this form (fig. 5) there is no distinction
between ectoplasm and endoplasm, and there is an entire absence of
vacuoles. The nucleus is central, and axial filaments were not seen.
The single specimen that I found looked much like a Suctorian of
the genus _Sphærophrya_, but the absence of a firm cuticle and the
presence of food-taking pseudopodia with granule-streaming makes it a
very questionable Suctorian, and 1 place it here until further study
throws more light upon it.
Diameter of body 40µ; length of pseudopodia 120 to 140µ.
[Illustration: Fig. 5.--_Actinophrys sol_.]
Genus HETEROPHRYS Archer.
The body is globular with but slight differentiation into ectoplasm
and endoplasm; one nucleus in the latter; contractile vacuoles
one or many; pseudopodia on all sides, thin, and with peripheral
granule-streaming; surrounded by a globular, rather thick coat of
jelly, which is hyaline inside and granular on the periphery. Fresh
and salt water.
Heterophrys myriapoda Archer. Fig. 6.
Synonym: _H. marina_ Hert. & Less. '74.
Diameter 25 to 80µ; pseudopodia twice as long as the body diameter;
the plasm often contains chlorophyll bodies (Zoochlorella). The
granular part of the gelatinous layer is thick (up to 10µ). The
spine-like processes are very thin and short. (Schaudinn '95.) The
marine form found at Woods Hole probably belongs to this species,
as described by Schaudinn. The short pseudopodia which give to
the periphery a fringed appearance are quite regularly placed in
connection with the pseudopodia. The latter are not so long as twice
the body diameter, the longest being not more than equal to the
diameter of the sphere. The body inside of the gelatinous covering
is thickly coated with bright yellow cells similar to those
on Radiolaria. The animal moves slowly along with a rolling
motion similar to that described by Pènard '90, in the case of
_Acanthocystis_. Diameter of entire globe 35µ; of the body without
the jelly 18µ. The extremely fine granular pseudopodia are 8 to 35µ
long. Common among algæ.
This form was probably meant by Peck '95, when be figured "a
heliozoön."
[Illustration: Fig. 6.--_Heterophrys myriapoda_.]