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 algae. 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 mu; largest diameter 125 mu.
[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 algae 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 mu by 270 mu.
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.