Marine Protozoa from Woods Hole | Page 3

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 42��, width 35��. 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 Trichosph?rium. I shall leave it here provisionally, with the hope that it may be found more abundantly another time.
[Illustration: Fig. 3.--Trichosph?rium sieboldi]
Genus GROMIA Dujardin '35.
(Dujardin 1835; M. Schultze '62; F. E. Schultze '74; Leidy '77; B��tschli '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 alg?. 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 245��; largest diameter 125��.
[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 alg? 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 230�� by 270��.
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 50��; 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