ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 629 



years, were found to be etched with stride, ending in edges transverse 

 to them; and near the apex of a spicule the projecting angles of 

 crystals are seen. In the case of sagittal spicules the paired rays 

 are etched, the unpaired is not affected. The author was able to 

 produce the etching, at will, by means of acetic acid. In section 

 acerates are oval or rhomboidal, and this serves to distinguish calca- 

 reous from siliceous spicules. This fact is an argument in favour 

 of Prof. Sollas's opinion that the Pharetrones are of a calcareous 

 nature. He concludes that the acerates of Calcispongias are built 

 up of excessively elongated primitive rhombohedrons of calcite. 



The perforate Foraminifera consist of calcite, judging from their 

 specific gravity ; whilst the Imperforata consist either of arragonite, or 

 if of calcite, this must be in combination with phosphate of lime, or 

 carbonate of iron. 



Artificial deposition of Crystals of Calcite on Spicules of Calci- 

 sponge.* — Prof. W. J. Sollas mentions the finding of sponge spicules 

 jncrusted with crystals of calcite, after standing for some days in 

 water containing an excess of calcium carbonate. They appeared to 

 have their optic axes orientated similarly to the calcite of the spicule. 



In a sagittal triradiate the crystals are confined to opposite sides 

 of the paired ray, and to the extremity of the unpaired ray. In 

 an acerate opposite sides for the whole length were incrusted ; thus 

 the crystals are deposited on the parts showing greatest liability to 

 solution, and the polarity which leads to solution appears to deter- 

 mine deposition. 



Sponges of Bohemia.f — Herr P. Frantisek gives an account of 

 various sponges. The first is Garterius stefanowii, which varies in size, 

 but may be 10 cm. long and 3 cm. broad ; the spicules are ordinarily 

 quite smooth and sharp at their tips ; the gemmules are spherical or 

 ellipsoidal, and have a high upper pole. The germ is protected by 

 an internal chitinous membrane, from which arises a cylindrical or 

 conical air-tube ; at its end there is a delicate crown-like appendage. 

 The inner membrane is covered by an air-chamber-layer, which 

 consists of small polygonal chambers, which are normally filled with 

 air. The amphidiscs are very numerous, and are provided with a 

 number of spines ; they are of two lengths, the longer of which, with 

 the crown at the upper end of the air-tube, forms an apparatus by 

 means of which the gemmules can attach themselves to foreign bodies, 

 and so be carried from place to place. This species was first found 

 in Russia by Dybowski, who, with a query, called it Dossilia 

 stefanoioii. 



Ephydatia bohemica n. sp. is found with Euspongilla lacustris ; it 

 is closely allied to C. stefanowii, but the gemmules have no air- tube, 

 and the amphidiscs are all of the same length. The author has 

 notes on Spongilla fragilis, Ephydatia muelleri, and Euspongilla 

 jordanensis. 



* Scientif. Proc. R. Dublin Soc, v. (1886) p. 73. 



t SB. K. Bohm. Ges. Wiss., 1886, pp. 147-74— German abstract, pp. 169-74 

 (1 Pi). 



