A. The fine fibrillæ in the cortical layer of the endoplasm were first described by Hertwig in 1879 (L. N. 33, p. 98, Taf x. figs. 6-10). He found them, however, only below the three openings in the capsule of the Tripylea, where they form three stellate groups of fibrils. I find them very clearly shown, and with especial distinctness, under the astropyle in most PHÆODARIA of which I have had the opportunity of examining well-stained and preserved central capsules. In many cases, also, the striation is not confined to the apertures, but spreads over the whole cortical layer. Perhaps this constitutes in all PHÆODARIA a thin myophane-sheet, whose contractile fibrils run from one pole of the main axis to the other and cause by their contraction changes in the form of the spheroidal central capsule.
B. The granular medullary portion of the endoplasm of the PHÆODARIA, with its numerous clear spherical vacuoles, was first described in my Monograph (1862), in the case of _Aulacantha_ (p. 263), _Aulosphæra_ (p. 359), and _Coelodendrum_ (p. 361) as a "finely granular, mucous substance (intracapsular sarcode), packed more or less closely with clear spherical vesicles from 0.005 to 0.015 mm. in diameter, each of which contains one or two, rarely three, dark shining granules." That these clear spheres are true vacuoles was first clearly proved by Hertwig (L. N. 33, p. 98). As a rule all the vacuoles of the same central capsule are of equal size (generally from 0.008 to 0.012 mm. in diameter), and are distributed at equal intervals throughout the finely granular endoplasm.
81. _The Components of the Extracapsulum._--The extracapsulum or extracapsular malacoma, under which name are included all those parts of the soft body which lie outside the central capsule, consists of the following constant, and important constituents:--(1) The _calymma_ or extracapsular jelly-veil; (2) the _sarcomatrix_ or layer of exoplasm immediately surrounding the membrane of the central capsule; (3) the _sarcodictyum_ or network of exoplasm, covering the surface of the calymma; (4) the _pseudopodia_ or radial fibres of exoplasm, which may again be subdivided into intracalymmar pseudopodia, uniting the sarcomatrix and sarcodictyum, and extracalymmar pseudopodia, radiating freely into the water outside the calymma.