REPORT ON THE DEEP-SEA KERATOSA. 55 



and transported into such totally different conditions of temperature, pressure, &c, 

 suffer greatly from this violent change. They are, in fact, almost knocked to pieces, 

 and their fine tissues are in a nearly deliquescent state." This is what Sir Wyville 

 Thomson says, when speaking of the gigantic Hydroid Monocaulus, and the same may be 

 said of the Stannomidse and their delicate symbiotic Hydroids. 1 



Indeed it was quite impossible, in spite of all possible precautions and different 

 methods of examination, to make out the anatomical structure of the canal-system of the 

 Stannornidse, and especially of the flagello-chambers. The dermal membrane, too, was 

 more or less destroyed. It is very probable that they agree in these particulars with the 

 closely-allied Spongelidse, with which they are closely connected by intermediate forms 

 (Psammophyllum). Nevertheless the composition of the well-preserved skeleton, and the 

 relations with the symbiotic Hydroids, are so peculiar, that they are sufficient for the 

 erection of a new family. 



Skeleton. — Accepting the term "skeleton" in the usual physiological sense as the 

 combination of all the solid parts of the body which serve as supporting and 

 protecting organs, due to their hard and firm consistence, we may say that the 

 skeleton of the Stannomidae consists of three different parts, viz. — (1) the delicate 

 spongin-fibrillse produced by the sponge itself; (2) the xenophya, or the foreign 

 enclosures (siliceous shells of Radiolaria, calcareous shells of Foraminifera, &c), all 

 received from the ooze of the sea-bottom ; (3) the ehitinous tubes of the hydrorhiza 

 of the symbiotic Hydroids, which replace the absent stout spongin-fibres. The two 

 latter elements, of course, represent a pseudo-skeleton composed of foreign enclosures, 

 whilst the first alone is the true skeleton proper of the sponge. But the most curious 

 fact is, that in all these Stannoinidse the main mass of the body consists of the pseudo- 

 skeleton, and that the fibres of the spongin-skeleton form only a delicate connective tissue 

 between the constituents of the pseudo-skeleton. The spongin-fibrillae appear as a 

 framework of fine elastic threads (/) strengthening the scanty maltha, which holds 

 together all the different parts of the sponge. (PI. II. figs. 1-3, in). 



Maltha. — The ground-mass of the mesoderm, which we briefly call maltha (the 

 mesogloea, mesenchyma, collenchyma, intercellular substance, common ground-mass, &c, 

 of other authors), is in all the Stannomidae scanty, and appears as a soft (clear and 

 transparent) structureless mass, cementing all the heterogeneous parts of the sponge 

 and its foreign enclosures together. The maltha has the same characters as in the closely- 

 allied Spongelidse ; it is clear and transparent, not granular, and contains two different 

 kinds of connective cells — (l) malthar cells, the usual small cells of the connective tissue, 

 roundish, spindle-shaped or stellate, with scanty protoplasm around the small nucleus ; 

 and (2) amoeboid wandering cells, probably migrating slowly through the whole body and 

 producing the fibrillar (similar to the odontoblasts which produce the dentin-fibrillse). 



1 Compare Zool. Chall. Exp., part lxx. p. 6. 



