172 



HARDWICKE'S SCIENCE-GOSSIP. 



[Aug. 1, 1S70. 



COMMON BRITISH SPONGES. 



f\T? all objects from the seashore there are none 

 ^ which appear to be so little studied, or so 

 imperfectly known as sponges. A few isolated in- 

 dividuals have devoted themselves to the subject, 

 and with them the study begins and ends. It is 

 quite true that the cabinets of most microscopists 

 contain two or three slides, labelled with mysterious 

 vagueness " Spicules of Sponge," but surely their 

 possessors would not claim the possession of any 

 knowledge of sponges, or they would never tole- 

 rate such " encumbrances." Pressed closely on the 

 point, and in nearly every case, the common com- 

 mercial sponge is the only sponge they are conscious 

 of having seen. Here and there a vague doubt may 

 exist, whether the beautiful Vcnus's flower-basket 

 (Eupleclella) is not a sponge, but it is not every one 

 who has arrived at this happy consummation Of 

 doubt. If one ventures to suggest " sponges " as 

 microscopic objects to be sought and brought from 

 the sea, it is at the hazard of an answer which once 

 greeted us, — " Oh, I can buy sponge at the oil-shop." 

 Alas ! poor man, his knowledge of sponges was not 

 burdensome. Beyond this there is, however, a 

 little advance amongst the majority of miscrosco- 

 pical students ; and to assist such in their annual 

 ' trip to the shore," we have resolved upon offering 

 a few suggestions. In the first place, we have no 

 English book which can be recommended to students 

 of these organisms. There is "Dr. Bowerbank's 

 Monograph of the British Spongiadse," published 

 by the Ray Society, and this has at least three 

 faults, as a student's manual. It is too large to be 

 handy ; it is too expensive for the ordinary micro- 

 scopist, who requires manuals on other subjects as 

 well; and it is by no means lucid in its descrip- 

 tions. In fact, it is more suited to the wants of 

 the professed man of science than the humble 

 student, and perhaps it is far from perfect even for 

 this. Sponges are not things which can be identi- 

 fied off-hand. It is absolutely essential that they 

 should be examined carefully under the microscope 

 before pronouncing upon them. In order to accom- 

 plish this, something, at least, must be known of 

 their structure, and the modifications which their 

 external form assumes. Finally, the examples of 

 sponges picked from the beach are dead, bleached, 

 and almost caricatures of the fresh and living 

 creatures brought up by the dredge ; however, such 

 as they are we purpose confining our observations 

 to such examples as may be found in moderate pre- 

 servation " cast up by the tide " ! 



To begin with one of the commonest, we will take 

 that which is known by the name of Chalina ocidata, 

 of which we give a figure (fig. 159). It is branching 

 or tree-like in its shape, often on the coasts of North 

 America more than a foot or sixteen inches in 

 length, but with us usually considerably less. It is 



variously branched, occasionally palmate or digi- 

 tate, with the branches rounded or compressed, and 

 the surface even. Orifices called oscula are arranged 

 somewhat in lines, and more or less on one side of 

 the branch. The margins of these orifices are slightly 



Fig. 159. Chalina oeulata, nat. size. 



elevated. The outer membrane contains a few 

 slender needle-like spicules. The spicules of the 

 interior or skeleton are shorter and stouter, and 

 rather spindle-shaped. When alive, this sponge is 

 yellow, with a tint of green, but when cast up upon 

 the sand, it is of the colour of whity-brown paper, 

 or rather darker than the sand. The accompanying 

 figure (fig. 160) will give a tolerable notion of the 

 appearance of a portion of a section of this sponge 

 under the microscope, with the spicules mixed up 



