ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
493 
ectoderm composing the sphincter being in immediate contact, and not 
separated by any jelly ; while the latter is, perhaps, due to the cells 
being passive and not active in the contraction. The author is of 
opinion that Dr. von Lendenfeld’s descriptions and figure of the ecto- 
derm cells are throughout erroneous. 
In the formation of pores the first stage is an ectoderm cell some- 
what more granular than most, and with distinct cell-limits. Such a 
cell grows inwards towards the endoderm, and pushes its way between 
the collared cells, while retaining a connection with the ectoderm. The 
cell then spreads out and becomes perforated. The fully formed pore is 
a single cell with a nucleus exactly similar to the remaining ectodermal 
nuclei, and an intracellular duct, which has a wide inner opening, and a 
very delicate outer opening. When the sponge contracts the pores 
close, and then, in section, look like amoeboid mesoderm cells. 
The spicules always have on each arm one, sometimes two cells ; 
each of these is closely applied to the spicule sheath ; the protoplasm is 
very clear, and it is often hard to see its limits. The impression made 
is that the spicules lie in a continuous cell network. The stellate cells 
of the mesoderm, so often described, are exceedingly rare, if not entirely 
absent ; what have been mistaken for them are the spicule cells, owing 
to the ordinary displacement of the spicules in sections. 
The collared cells vary in shape, according as the sponge is con- 
tracted or expanded. In the normal condition they are without any 
projections, but, when observed living, they can often be seen to throw 
out numerous fine processes ; this is always a sign of cessation of activity 
and of death. Lendenfeld’s figures, therefore, appear to represent ab- 
normal and pathological phenomena. 
The principal method employed by the author, and one that has 
been fruitful of good results, was careful examination of surface views of 
pieces of the wall of the sponge, always preserved quite fresh from the 
sea on board the fishing-boat. 
Adriatic Sponges.* — Dr. R. von Lendenfeld continues his mono- 
graph, discussing the calcareous forms. Of these there are 32 species, 
eight new. The author describes their distribution, and gives a key to 
the genera, and to the perplexing synonomy. He then proceeds to a 
systematic account of the canal system, the skeleton, and the minute 
structure. His classification is as follows : — 
Typus, Spongise. Classis Calcarea. 
Ordo I. Homocoela. Family 1. Asconidee, Ascetta , Ascandra , 
Ascyssa. 
„ 2. Homodermidse, Hometta , 
Homandra, Homoderma. 
„ 3. Leucopsidas, Leucopsis. 
II. Heterocoela. „ 4. Syconidse, Sycantha , Sycetta , 
Sycandra , Grantia , Grantessa , 
Ute, Amphoriscus , Ebnerella. 
„ 5. Sylleibidae, Polejna, Vosmaeria. 
„ 6. Leuconidse, Leucetta , Leucandra f 
Leucyssa, 
* Zeitschr. f. Wiss. Zool., liii. (1891) pp. 361-433. 
