its component vesicles. Not unfrequently, this superficial skeleton comes to constitute a spherical shell, or a system of concentric or otherwise associated spheres.
We have already learned that a great part of the body of the Radiolarian, and especially that outer portion to which Haeckel has given the name of the ãcalymma,ã is built up of a great mass of ãvesicles,ã forming a sort of stiff
froth, and equivalent in the physical sense (though not necôÙesôÙsarôÙiôÙly in the bioôÙlogôÙiôÙcal sense) to ãcells,ã inôÙasôÙmuch as the little vesicles have their own well-defined bounôÙdaries, and their own surôÙface phenomena. In short, all that we have said of cell-surôÙfaces, and cell conôÙforôÙmaôÙtions, in our disôÙcusôÙsion of cells and of tissues, will apply in like manner, and under apôÙpropôÙriôÙate conôÙdiôÙtions, to these. In cerôÙtain cases, even in {468} so comôÙmon and simôÙple a