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spicular network of its membrane, looking like a piece of lace, and it is 

 within the area thus defined the pores may easily be seen. It is not, how- 

 ever, in the fresh state they can be so well observed. This sponge is very 

 Protean in its form and colour, showing how little one can depend upon 

 either character in this class. After a storm, I picked up at Teignmouth, 

 fresh from the sea, one of olive green, another of orange, and another of 

 yellow colour. It is found coating, or parasitic, sometimes very massive, 

 but it is usually embracing portions of some small Algre, and developing 

 upon and enclosing them. H. incrustans — well so termed, for it is so often 

 found upon shells or Algse, or pieces of rock in crevices, preferring a 

 shelter. It is in every way a most interesting sponge, having a somewhat 

 more regular rete than that of " panicea," and rejoicing in a great 

 variety of spicular forms. It is in this last particular a very useful 

 sponge for the young student to study, and will prepare him for rarer 

 species. The stellate spicule does not appear in this genus, though most 

 of the other forms abound, and in great variety. 



There is now a genus to be noticed as one to be generally distinguished 

 by its outward branched form, and its stiff, rigid character. This will show 

 it sufficiently, but its skeleton analysis is nevertheless required, especially in 

 distinguishing species. Its name, Dictyocylindrus, implies a cylinder net- 

 work. Long and stout acuate spicules, loosely compacted together, almost 

 parallel to the axis of the branches, but diagonally making an indefinite 

 rete, and not as in Desmacidon, making a multi-spicular solid fibre, is 

 characteristic of the skeleton, in which are disposed at right angles small 

 spined acuate spicules. Variations of the form of the long acuate spicules 

 occur in different species, sometimes being very irregular and out of sym- 

 metry. JJ. ramosus is common and characteristic of the genus in outward 

 form. D. stuposus and B. fasciculosis have each forms of stellate spicules, 

 but no anchorate or other form of flesh spicule are found in any of the 

 genus. Another genus, which stands by itself, and is to be generally known 

 by its outward form, is Polymastia (many whips). It gets its name from, 

 its surface displaying, sometimes in great numbers, projecting thong-like 

 elevations, which seem to be flexible, and thus warrant the " scourge " term 

 applied. But as in all cases in studying this class of organisms, the interest 

 is in the intimate skeleton structure. This is composed of very compact 

 columns of spicules, symmetrically formed, braced together by transverse 

 fascicules, which sometimes very regularly cross at right angles to the 

 columns, associated also with spicules, not so regularly arranged. In this 

 there is an alliance in form with the beautiful Eiiplectella a&pergillum, 

 though, in this latter, there is no such separation of distinct spicules of the 

 skeleton, the latter being anchylosed, as one might say, and which, perhaps, 

 may take place during its growth. 



The last group of siliceous sponges which require to be taken into con- 

 sideration, are in close alliance with each other, not only in general character 

 but in the details of spicular forms. These are Geodia, Tethya, Pachyma* 

 tisma, and Ecionemia, and it is generally considered, that they have a higher 

 claim in organization. The skeleton spicules, which constitute and build up 

 Journ. Q. M. C, Series II., No. 8. g g 



