ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
343 
relation of parts. It is possible to bring two animals into a state of 
l)ermanent fusion if they are attached to one another by means of bristles, 
or if one is placed in the other. 
Evagination of Hydra.*— Herr M. Nussbaum discussing this com- 
munication of Herr C. Ischikawa’s, remarks on the changes which ensue 
when a Hydra is turned inside out. He restates his old conclusion ^ 
that ectoderm does not become endoderm, nor vice versa ; on the con- 
trary, the ectoderm along with the middle lamella and with the endo- 
derm as well, grows over the evaginated original endoderm, in a fashion 
also observed in wound-healing. Complicated processes of coalescence, 
absorption, and fresh growth restore the polype to its status quo. 
Nussbaum maintains that Ischikawa has only corroborated the above 
explanation, although he has sought to contradict and correct it. 
Initial Cells of Ovary of Freshwater Hydra. | — M. J. Chatin finds 
that those observers have been misled who have asserted the presence 
of free nuclei in the ovary of Hydra. When suitable methods, such as 
the use of solution of dahlia, followed by weak acetic acid, are applied 
these nuclei are seen to Lave a delicate layer of protoplasm around 
them. 
Porifera. 
Deep-sea Keratosa of the ‘ Challenger.’§— Prof. E. Haeckel gives 
an account of some remarkable organisms w'hich have been assigned to 
various divisions of the animal kingdom. They have been curiously 
modified by symbiosis with a commensal organism which is very 
probably in most cases (if not in all) a Hydropolyp stock. Eleven 
genera and twenty-six species, all of which are new, are described in 
this report. 
Old and new Questions concerning Sponges. |1 —Mr. A. Dendy, 
under the above heading, deals with some problems in the structure of 
sponges. In answer to Dr. v. Lendenfeld, he does not contend that 
“ Soil as’ membrane” is found in all Sponges, but it is most certaiuly 
present in Stelospongus JldbelUformis ; while some of Mr. Dendy’s figures 
were diagrammatic, others were as exact representations of actual pre- 
parations as he was able to produce. Turning next to Dr. Polejaeff’s 
statement that we must consider the horny sponges as a palseonto- 
logically ancient group, he gives a statement as to his own observations 
on Siphonochalma, in which genus there are three species which nearly 
resemble one another in external form. S. spiculosa has large and very 
numerous spicules, S. procumbens has three distinct and abundant, while 
S. ceratosa has the spicules excessively small and slender, and reduced 
to the merest vestigial structures imbedded in the stout horny fibres. 
In S. plicifera and S. maxima some specimens may sometimes contain 
vestigial traces while others are entirely destitute of spicules. It is 
impossible to assert that some horny sponges, at any rate, are not 
descendants of siliceous Chalininje. 
* Arch. f. Mikr. Anat., xxxv. (1890) pp. 111-20. t Op. c., xxix. 
X Comptes Rondus, cx. (1800) pp. did-O. 
§ Reports of the Voyage of H.M.S. ‘Challenger,’ xxxi., I’art Ixxxii. (1880) 
02 pp. and 8 pis. H Zool. Anzeig., xiii. (1800) pp. 14-7. 
