ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
459 
is formed by tlie growth of these selfsame septa in a horizontal direction, 
and the intercalation of one or two orders, in addition to those already 
existing, and that the whole coral structure of the adult Fungia is directly 
derived from the pre-existing similar structures in the trophozooid or 
antlioblast. 
With regard to the presence or absence of a theca, Mr. Bourne is 
opposed to Ortmann, and is on the same side as Yon Koch ; he declares 
that from the first the young Fungia has a compact lateral theca which 
is not porous, is not formed by casual fusion of synapticulae, and is 
represented by a basal theca in the adult. 
The detachment of the anthocaulus appears to be due to a degenera- 
tion of the tissue-cells in the region where detachment takes place, and 
the decay of the corallum appears to follow on the degeneration of the 
tissues. This view is based on the assumption that the hard parts of 
the living coral are in some manner intimately connected with the living 
protoplasm of the tissues, and that their integrity is dependent on the 
integrity of the tissues which give rise to them. At any rate, in any 
coral a marked distinction can be observed between those parts of the 
corallum which are clothed by the living tissues of the polyps and those 
which are not. The former are pearly white, translucent, and very hard ; 
they seem to be more resistant to the action of solvents, and especially 
to the attacks of boring parasites ; Aclilya penetrans , for example, is an 
invariable accompaniment of the detachment of the anthocyathus. 
Between such coral and that which has been deserted by living tissue, 
microscopical examination shows no difference in structure, the greater 
transparency and the more distinctly crystalline structure being the only 
feature of the former. 
In conclusion, some of Dr. Ortmann’s generalizations are criticized, 
and it is pointed out that he has been led to adopt an untenable hypo- 
thesis by neglecting the salutary rule that, in the explanation of adult 
structure, due weight must be given to developmental history. 
Structure of Tentacles of Apolemia uvaria.* — M. Y. Willem has 
investigated the tentacles of this Siphonophore ; they have a central 
cavity which has at its free end a hitherto unnoticed orifice, which pro- 
bably serves for the evacuation of some effete products. The cells of the 
lining endoderm vary in character in different parts, but they are chiefly 
absorbing in function, and the author has been able to trace into them 
the fluid substances digested by the gastrozooids, and injected by them 
into the general nutrient system of the colony. The funnel-shaped cells 
are provided with a vibratile flame which drives the nutrient substances 
into them, and they are, therefore, not excretory, as Chun thought, but 
absorbent. Other absorbing cells have a simpler mechanism, fatty 
globules penetrating directly into them. More distally in the tentacle, 
there are three longitudinal pads which can close the cavity ; the cells 
of these are able to emit fine pseudopodia which seize on nutrient 
particles. Still more distally the cavity dilates, and here disintegrated 
particles are found, which probably escape by the terminal orifice. 
Regeneration in Obelia.f — Mr. C. B. Davenport has experimented 
on Obelia commissuralis by cutting it at different levels in order, if 
* Bull. Acad. Roy. Belg., lxiv. (1894) pp. 354-63 (1 pi.). 
f Anat. Anzeig., ix. (1894) pp. 283-94 (6 figs.). 
