BIOLOGY. 
Spong. 5 
II. BIOLOGY. 
1. MORPHOLOGY and PHYSIOLOGY. 
a. General [cf. Titles 8, 10, 13, 16, 25]. 
Evans (10) and Maas (25) describe mitotic cell-division in Sponges. 
According to Evans the collar-cells of the ciliated chambers of Spongilla 
multiply mitotically. The nuclear spindle which lies parallel to the 
chamber wall can be best seen in the cells of free-swimming larvae. 
There appear to be 12 chromosomes. A centrosome could not be clearly 
made out. The chromatin forms a plate which divides into two. Each 
daughter-plate travels to its spindle-pole. There it forms first a ring and 
then a cup. Finally, whilst the cell divides, it is disintegrated and 
converted into small granules. According to Maas mitosis is met with in 
the ova when extruding the polar bodies and in the first cleavage cells of 
Sycandra raphanus. 
On account of the reversion of the embryonic layers Delage & 
Herouard (8) propose to replace the usual terms “ ectoderm ” by “ epi- 
derm” and “entoderm’ by “epithelium atrial.” For the interstitial 
layer they employ the term “ mesoderm.” The gastral cavity is termed 
“atrial” cavity. 
Haeckel (16) gives some figures of artistically beautiful structures in 
Calcareous Sponges. 
Girod (13) publishes a short general account of the Spongillidee. 
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b. Canal system [cf. Titles 8, 10]. 
According to Evans (10) the incurrent pores on the surface which lead 
into the subdermal cavities are, in Spongilla , larger than the chamber- 
pores. Both are intracellular. The chambers of Spongilla multiply by 
division. 
Delage & Herouard (8) give a general, extensively illustrated account 
of the different forms of the canal-system in Sponges. 
c. Skeleton [cf. Titles 4, 5, 8, 9, 23, 26, 39, 43]. 
Evans (9) does not accept the distinction between microscleres and 
megascleres in the usual sense and thinks it not improbable that—in 
Spongilla at least—the former are young stages of the latter. 
Delage & Herouard (8) publish a list of terms of sponge spicules with 
illustrated definitions. These terms are on the whole in accordance with 
the terms proposed by Schulze & Lendenfeld. 
Chun (5) has discovered a hexactinellid Sponge comparable to Hyalo- 
nema in which however the spicule-root-tuft is replaced by one single 
spicule of enormous dimensions. The largest spicule of this kind observed 
whole is H metres long and as thick as a pencil. Fragments of the 
diameter of a human finger also brought up by the trawl are parts of such 
spicules which were originally most likely 4 or 5 metres long. These 
sificules are composed of concentric layers of silica. 
Lister (23) has a note on the skeletal elements of Astrosclera. 
Topsent (43) found in Stylotella inornata masses of foreign bodies, 
chiefly sand-grains, which form an important part of the skeleton of that 
sponge. 
Butschli (4) and in a more detailed manner Sukatschoff (39) describe 
the structure of the fibres of Horny sponges. In Hircinia the latter finds 
