180 B. W. PRIEST ON THE STATOBLASTS OF 



until they attain full dimensions. These additions are generally 

 made more quickly at one point than another, rather than through- 

 out their entire length, so that in their half-developed condition 

 they present one or more bead-like inflations, which disappear when 

 the growth is complete. 



11 When the growth of the sponge-mass has made some progress, 

 the formation of a distinct investing membrane out of what was 

 the flat transparent border, becomes obvious. This membrane is 

 gradually detached from the central ova-bearing cells, either by the 

 shrinking of the latter, or by the protrusion of bundles of spicules 

 which force it outwards, leaving here and there open spaces 

 between the membrane and the central cell mass. 



" And so it proceeds until after the development of other 

 spicules and canals formed for the passage of the water, the 

 Sponge is perfected and continues to grow by adding to its general 

 structure, until it arrives at its full size, which of course varies 

 according to the locality and species. 



" The process best suited for examining the structure of the 

 Statoblasts in the dry state — which is the most easy method, many 

 difficulties attending the examination fresh, when attainable 

 — is to place four or five on a glass slip with a drop of strong 

 nitric acid. Boil this to dryness over a very low spirit lamp. 

 Do this three times. Then place the slip on the incline and pass 

 water over it with a camel's-hair pencil until all the remains of the 

 acid is washed out. Next with a sharp, thin knife like a lancet, 

 divide, in half or in quarters, one or two more Statoblasts, and 

 adjust them round the remains of the foregoing (or on a separate 

 slip if you prefer it.) Add a drop or two of benzole or turpentine 

 to keep them in place, and when dry, which will be in a few 

 minutes, add a drop of Canada balsam, cover with thin glass, 

 previously just warming the cover, put the slide in a warm place 

 for some hours to harden, and it will then be ready for examina- 

 tion." 



I trust that what I have called attention to this evening may 

 prove as much a source of interest to those members who should 

 take up the subject as it has been to myself.* 



* After reading the above paper, Mr. Frank Crisp and Mr. Alphens 

 Smith kindly called my attention to notices in the " Transactions of the 

 Linnean Society," and in "Nature," of two new Freshwater Sponges 

 discovered in Australia, and described by Mr. W. A. Haswell, viz., Spon- 

 yilla sceptroides and Spoyigilla botryoides. 



