INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 661 



There can be no doubt that the modification was gradual — probably 

 brought about by tlie ancestors of the fresh-water Medusa penetrating 

 higher and higher through the brackish waters of estuaries into the 

 fresh water of rivers — and it would, the author thinks, be hard to 

 point to a more remarkable case of profound physiological modifica- 

 tion in adaptation to changed conditions of life. If an animal so 

 exceedingly intolerant of fresh water as is a marine jelly-fish, may yet 

 have all its tissues changed so as to adaj)t them to thrive in fresh 

 Water, and even die after an exposure of one minute to their ancestral 

 element, assuredly we can see no reason why any animal in earth or 

 sea or anywhere else may not in time become fitted to change its 

 element. 



Porifera. 



Sponges of the Leyden Museum.* — In this, the first part of his 

 communication (written in English), Mr. Vosmaer deals with the family 

 of the Desmacidinidfe. As is well known, these and all the siliceous 

 sponges are not only difficult to determine on account of their great 

 variability, but from the technical objection that Bowerbank and 

 Schmidt, two leading authorities, worked almost simultaneously, and 

 altogether independently of one another. After giving the palm to 

 Schmidt, the author describes the symbols he employs in his descrip- 

 tions, and then passes to a description and enumeration of the species ; 

 of these he gives 165, some of which are new, and these he places 

 in sixteen genei-a, three of which, Ainphilectns, Crnmhe, and Hastatus, 

 are new ; the characters of some of the others are emended. The 

 paper seems from the remarks which the author makes on the varia- 

 bility of species, to be a distinct advance on most essays on the 

 subject which have appeared in the English language. 



Structure and Affinities of the Genus Protospongia, Salter.f — 

 Mr, W. J. Sollas describes the character of the Cambrian genus 

 Protosjoongia from the original and other specimens. In Dr. Hicks's 

 specimen the spicules of the sponge show their original form, when 

 it is clear that they are not fused together into a continuous network ; 

 thoy form a network only by the interlacing of tlicir extremities. 

 The spicules arc quadriradiate, with the centre raised, so that each 

 spicule indicates the outlines of a low four-sided pyramid, the centre 

 being at the apex, and the four rays representing the four edges of the 

 pyramid. The rays do not diverge at right angles, and thus the base 

 of the pyramid is oblong, though this may be due to distortion. From 

 some indications the author is inclined to believe that a fifth ray may 

 have sprung from the centre of the spicule downwards. The rays of 

 the spicules appear to be cylindrical. The spicules are generally of 

 seveial sizes, the larger ancs foiming a framework which is filled 

 in by the smaller forms, tlic latter being regularly arranged, so that 

 the smaller ones fill up the S(piare spaces left between the rays of the 

 larger, and thus build up a network of square meshes gradually 



* 'Notes R. Mus. Nrtherlands ' (ii. 1880) p. 99. 



t ' Abstr. Prc)c. Geol. 8oc. Lend.,' No. 387 (1880) p. 1. 



