ANATOMY, HISTOLOGY, AND GENERAL. SpOlig. 9 
Sponge, allied to the Spirastrellidce. The sterrasters bear only a super- 
ficial resemblance to the Geodidce , their structure and development are 
monaxonid. 
Von LENDENFELD(27)has written a monograph on the Tetractinellida of 
the Adriatic. The first part contains a detailed description of the species, 
of which there are twenty-six, including one Lithistid. Two species are 
new. A table showing the geographical distribution, and an analytical 
key to the species are given. The synthetical part treats of the indivi- 
duality and external form of tetractinellid Sponges, their canal system, 
cortox, and skoleton. A numbor of new names for spicules is 
suggested. The epithelium, according to Von Lendenfeld, may be 
of various forms, — pavement epithelium, with or without flagella, 
spherical, conical, and columnar epithelium. Mushroom-shaped epithelial 
cells, as described by Bidder and Minchin, seem to occur amongst the 
Tetractinellida in exceptional cases only. With regard to Sollas’s mem- 
brane, the author cannot convince himself that it is present in the normal 
condition. Osmium-material of Oscarella showed distinct collar and 
flagella without Sollas’s membrane, but material treated only with spirit 
showed no flagella, the collars were less well preserved but were fused to 
form a Sollas’s membrane. [Compare Vosmaer & Pekelharing (63) and 
Bidder (3).] Hereafter follow description of cortex, chones, pulp, and 
a note on the development. 
Rauff (36) describes the process of fossilization of certain Sponges, in 
which reversion of the original conditions has taken place in such a 
manner, that the original silicious skeleton has been changed into cal- 
careous spar, and the calcareous sediment into pure silica. Rauff explains 
it as follows : — After the death of the animal, and the decomposition of the 
soft parts, the silicious skeleton was slowly buried iu the mud of the sea, 
the mud permeating and filling up the spaces between the framework of 
the skeleton. Gradually the sediment hardened into rock. Then the 
rock was permeated by solutions which dissolved the original silicious 
skeleton, but did not affect the calcareous sediment. Thus, in the place 
of a silicious skeleton, a continuous system of fine tubules was formed, 
which preserved the outlines of the skeleton in the sharpest detail. 
Afterwards the tubules were filled up with calcareous spar, and it was 
only after this took place, and when the rock was permeated by silicious 
solutions, that the ground mass became changed into clear chalcedon, 
which enclosed the water-clear calcareous skeleton, often of extreme 
beauty. 
Rauff (40) publishes the first part of a Monograph of Fossil Sponges. 
The present part is introductory, and begins with an account of the 
literature between the years 1672 and 1892. Subsequently the mor- 
phology of Sponges, their external form, histology, canal system, sexual 
and asexual reproduction, skeleton, and classification, and, lastly, the 
conditions of the fossilization are given. The author has fully 
utilised the labours of his predecessors, and his work will no doubt be a 
great assistance to those interested in this branch of zoology. 
