50 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and of numerous glandular cells (tlie “ goblet-cells ”) in its lower 
part ; a median zone is characterized by the presence of numerous 
gland-cells ; while the blastostyles and the region of the foot have the 
endoderm almost exclusively composed of vacuolate cells, usually loaded 
to the full with stored nutritive material in the form of nutritive 
spheres. The nutriment formed in the cnteron appears to be conveyed 
through the organism by means of the somatic fluid. 
Tectological Studies on Hydroids.* — Dr. Hs. Driesch finds that the 
main stem of Antennularia is formed from an indefinite number of tubes 
inclosed by ectoderm and endoderm, and communicating irregularly. 
The plumules are arranged in alternating whorls, varying in number 
within definite limits in the different species, and increasing as the 
colony grows older. There is no relation between the number of tubes and 
the longitudinal series of plumules. The young form of Antennularia is 
for the most part plumularoid. 
Origin and Development of the Reproductive Cells in Tuhularia.t 
—Dr. A. Brauer, having investigated Tubularia mesembryantJiemum, 
finds that the generative cells arise from interstitial cells of the ectoderm 
in the gonophore-stalks. Near the origin of a gonophore they pass 
into the endoderm, and migrate thence to the place where they 
mature, namely, the ectodermic manubrium ( Gloclcenkern ). The form 
and position of the ovum in the gonophore vary much. The segmenta- 
tion may take place in one of two ways. Each nuclear division may 
be followed by cell-division ; or it may be that at first only the nuclei 
multiply and that this is followed by a gradual segmentation which 
begins at the directive pole and extends towards the opposite side. 
In the first case, a coeloblastula is formed, and the endoderm is 
established by division of the blastoderm cells. In the second case the 
formation of the endoderm begins before the segmentation is finished. 
The endoderm arises in a multipolar fashion ; its cells obliterate the 
segmentation-cavity, and there results a many-layered solid embryo. 
This has been erroneously termed a morula, for it represents not the 
final result of segmentation, hut the two-layered embryo. By division 
the ectoderm forms the interstitial layer. The tentacles are incipient 
before the appearance of the central cavity which is formed by diffiuence 
of endodermic cells. As the two layers are histologically differentiated, 
the supporting lamella becomes recognizable. 
Porifera. 
Siliceous Spicules of Geodia.J — Dr. R. v. Lendenfeld directs special 
attention to a more or less close network of freely projecting spicules 
which he has found in Adriatic Geodise, and which have, as yet, been 
only slightly described. At a depth of from 15 to 3 ’5 mm. above 
the surface lie the centres of these spicules, whence the branching-rays 
are given off ; the shafts of the spicules are long, thin and curved. 
The author concludes that the primary axis of the Tetraxonia is 
homologous with the single axis of the Monaxonia. 
* Jenaisehe Zeitsehr. f. Naturwiss., xxv. (1891) pp. 467-79 (3 figs.). 
t Zeitsehr. f. Wiss. Zool., lii. (1891) pp. 551-79 (3 pis.). 
j Zool. Anzeig., xiv. (1891) pp. 207-9. 
