Knowledge of the Freshwater Sponges. 99 
Zeiss V. oc. 2, obj. C). a. External amphidiscus-layer; 0. 
Granular parenchymatous layer; c. Inner amphidiscus-layer ; 
d. Chitinous membrane ; e, Germinal corpuscles. 
Figs, 3-6. Trochespongilla erinaceus, Ehy. 
Fig. 3, Arrangement of the gemmules in the intermediate layers of the 
lamelle. a, Air-chamber layer, representing the natatory ring 
of the statoblasts of the freshwater Bryozoa; 6. Chitinous cap- 
sule ; c. Aperture of the gemmule. 
Fig. 4. Structure of the air-chamber layer on the surface. 
Fig, 5. Median longitudinal section through a gemmule (magn. Zeiss V. 
oc. 2, obj. C). 0. Aperture; a. Air-chamber layer; 6. Amphi- 
discus-layer; ¢. Chitinous capsule ; d. Germinal corpuscles. 
Fig. 6, Longitudinal section of the air-chamber layer (magn. Zeiss, oc. 2, 
obj. EK). a. Air-chambers; 6. Amphidiscus-layer. 
Remarks by H. J. Carrer, F.R.S. &e. 
The foregoing translation of a “Résumé” in German, 
which is appended by Dr. Franz Vejdovsky to his “ Contribu- 
tions to the Knowledge of the Freshwater Sponges,” read at 
the Society of Sciences in Prague on the 12th of October last, 
and subsequently published in the Bohemian language, is 
of much interest, because it points out additional instances of 
what has been seen in other treshwater sponges, viz. Parmula 
Batesii, Spongilla nitens, and S. alba (‘ Annals,’ 1881, 
vol. vii. pp. 99, 89, and 88, pl. v. figs. 1 and 3, respec- 
tively), together with a new variety in structure. ‘Thus, in 
his Ephydatia amphizona (syn. Eph. Miillert, forma B) we 
have an illustration (Pl. VI. fig. 2) of what occurs in the sta- 
toblasts of the two former, viz. a layer of statoblast-spicules 
on each side of the “ crust” ( Annals,’ 7. c. p. 83), here com- 
posed of the “ microcell-structure” (¢b. 7b. pl. v. fig. 2, a) ; 
while in his Trochospongilla erinaceus (Spongilla erinaceus, 
Ehr.) is another example of what occurs in Spongilla alba 
(‘ Annals,’ 2. c. p. 88), viz. a mixture of spicules with the 
“ microcell-structure,” but in a new form,, that is, instead of 
the crust being composed of microcell-structure charged with 
statoblast-spicules only, as in Spongzlla alba, it is made up of 
comparatively large cells, like that in Spongilla nitens, &c., 
(‘ Annals,’ Z. c. pl. v. fig. 3, ¢), arranged in a columnar form, 
but traversed by full-sized skeleton-spicules of the species, and 
finally united to a layer of birotulates which are fixed to the 
“ chitinous coat” (Pl. VI. figs. 5 and 6), yet so tenderly 
that, whether on account of this or the intermingling of the 
ends of the skeletal spicules which project beyond the cell- 
structure with the rest of the sponge, it very often happens 
that, in endeavouring to extricate the whole statoblast, the 
cellular crust &c. remains, while the chitinous coat and its 
layer of birotulates (amphidiscs) come away without it. 
