1 2 For if era. 



tissue. As to its hydrostatic value , the dried gemniules of all species float ; of 

 freshly liberated genimules some sank and some rose to the surface, all developed 

 alike. Probably few float of those naturally liberated, as gemmules are very rare 

 in fresh-water plankton. The amphidiscs of this layer have been held to be 

 perforated, in old dry geinniules this is the case. An outer cuticle is generally 

 present, in Ephydatia fluviatilis some only of the gemmules in a given specimen 

 may possess it, while sometimes a second layer of amphidiscs stands outside it ; 

 in E. millleri are 2 or 3 layers of amphidiscs, but no outer cuticle. - The soft 

 contents have no proper inembraue within the inner cuticle. In the ripe gern- 

 mule there is no trace of flagellate chambers or flat epithelium, though spicules 

 [cf. supra p 7 Maas( 2 )] are formed; the cells are rounded, often spherical, but the 

 polyhedral aspect described by Marshall and others is found when gemmules in the 

 act of leaving the capsules are preserved in alcohol. The yolk-granules differ 

 from those of the ovum and embryo in being smaller, generally lens-shaped, and 

 homogeneous ; they react differently with acetic acid or stains; Kleiuenberg's compar- 

 ison of the ovum granules with the pseudocells in Hydra appears just [cf. supra 

 p 7 Maas ( 2 )] . The yolk-granules of the gemmules must represent the starch-gra- 

 nules of Carter and others, but contain no starch ; nevertheless, since Zoochlorellae 

 occur in them, starch may sometimes be present. Starch occurs in the vesicular cells 

 vfEph. millleri when no green bodies are present. - - The gemmule during formation 

 contains cells (1) naked and amoeboid, mostly more or less full of yolk-granules ; (2) 

 with fine equal granules like the nutritive cells of the ovum; (3) with large unequal 

 granules, like the unequally granular cells of the parenchyrn : all have one nucleus 

 with uucleolus. In the fully-formed gemmule all cells are equally full of yolk, no 

 more amoeboid, with a delicate cell-membrane. In winter some or all cells have 2 

 nuclei (occasionally more), they are double the size of those remaining with one 

 nucleus. Before escaping from the capsule the cells become again amoeboid ; no 

 intercellular substance could be found until a few hours after escape [cf. Maas, I.e.]. 

 Lieberkuhn found the cells of the fully-formed gemmule behave differently in 

 water and saliva ; W. finds that in each alike the yolk-granules escape through the 

 cell-membrane, the protoplasm swells, the nucleus or 2 nuclei become visible, and 

 the cell membrane finally bursts. Cells from a gemmule taken in the act of leav- 

 ing the capsule usually swell without escape of yolk, and are more actively amoe- 

 boid. The number of cells in one gemmule of Sp. fragilis was found to be 385, 

 the relative proportion of those with 1 or 2 nuclei varies greatly ; sometimes a 

 solitary nucleus shows 2 nucleoli. Diameters of cells were measured from 0,012 mm 

 to 0,057mm. W. appears now to reject his former view ( 6 ) that fusion produces 

 the biuuclear condition, and to ascribe it to mitosis preceding cell-division 

 [cf. Maas, 1. c.]. Gemmules taken ripe in the autumn, ubei'winterten, or in act 

 of escaping, showed well defined cells whether examined fresh or preserved (al- 

 cohol or corrosive sublimate) ; from September to April [apparently with excep- 

 tion of gemmules of the previous year] the contents showed a mass of nuclei, 

 protoplasm, and yolk-granules, without cell-boundaries. - - Green gemmules 

 of Euspongilla lacustris. The habitus of the 4 fresh- water sponges in the Tegeler 

 See (near Berlin) is described , particularly as regards the necessity of light to 

 produce the green colour. Eph.fluv. was found with gemmules for the first time 

 in 8 years researches on this species. Gemmules in the grey or brown Sp. fragilis 

 appear as white spots , showing no green granules ; in the green Eu. lacustris as 

 bright green spots , in which the uninuclear cells show among the yolk-granules 

 Zoochlorellae. These are of two sizes, 0,00125 mm and 0,0024 mm in diameter, 

 corresponding closely with Zoochlorellae measured from the mesoderm of Eph.Jlu- 

 viatilis] Brandt's method failed to show any nuclei. Though not traced, W. 



