Z 3. Q. WALLER ON A NEW BRITISH SPONGE 



which arc distinct and more or less interesting ; and that which he 

 now calls Microciona plumosa has long been known to our 

 naturalists, having been first described by Colonel Montague, who 

 must have been very familiar with Paignton shore, under the name 

 of Spongia plumosa. Here it grows abundantly, often in large 

 patches, of a deep orange-red colour. Most of the genus hitherto 

 described are found to range from a deep yellow to the deepest 

 blood-red, as in M. atrasanguinea ; but that which I am about to 

 describe is of a deep olive green when living, and of a pale olive 

 tint when dry. So in colour it is distinct from all its congeners. 

 But every student of the Spongiadas knows that colour is a variable 

 condition, and one must never rely on its being constant, when only 

 one example has been discovered, as in this instance. Were this, 

 then, the only difference, it could not stand as a variety. Fortu- 

 nately, there is a structural distinction, which leaves this matter in 

 no doubt whatever. Amongst the various forms of retentive 

 spicules, none of the sponges of this genus, at present made known, 

 have the bihamate form common to a large number of the silicious 

 sponges. So, as these are found upon the membranes of the example 

 under consideration, it is clearly a well-marked variety. 



The small coating sponges, not only belonging to this but to allied 

 genera, well deserve the attention of microscopists ; for without the 

 microscope many would be utterly lost to us ; and all require that 

 instrument to detect and display the minute and curious forms of 

 spicula which are discoverable in their tissue — almost as difficult of 

 resolution, and certainly as interesting, as the markings of the 

 Diatomaceas. Many of the Microciona, with the long flexuous 

 columns of their skeleton, are singularly beautiful objects under the 

 low powers, and cannot fail to interest the most common observer. 



The sponge before you is but a small portion of that I discovered, 

 but it was with difficulty I obtained it from its narrow secluded 

 habitat. As you see, it covers a piece of the Red Sandstone, very 

 thinly ; its stoutest part not rising above the eighth of an inch, 

 whilst the average thickness is less than half that. Alive it was 

 smooth, slightly undulating, sarcode abundant, neither oscula nor 

 pores very distinct, the former few in number. In the dried condi- 

 tion, the oscula are more easily discernible ; they are dispersed and 

 generally separate, but sometimes two are found together. 



The skeleton columns are in length intermediate, not being quite 

 so long as in M. plumosa, when the latter is fully developed and they 



