66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



"candelabra" are absent. This last-mentioned form has quadri- 

 radiate spicules, and these, as also the tri-radiate foi-ms, take on an 

 anchor-shape in the cortical layer. 



Dysideidae and Phoriospongiae.* — Dr. W. Marshall gives an 

 account of these two groups of sponges, which appear to have no 

 specially close relation to one another, although they are both 

 remarkable for the fact that they take up foreign bodies to aid in the 

 formation of their skeletons. Almost all the material which the 

 author studied came from Australia, and was handed over to him 

 by Professor Haeckel, who has himself worked a good deal at these 

 forms. 



After an introduction, in which the history of the knowledge of 

 these sponges is reviewed, the following definition of the Dysideidsa 

 is given : they are horny sponges, in which the capacity of adding to 

 their skeleton by the accumulation of foreign bodies is carried to an 

 extreme. It is very rare for even short pieces of fibre to be found 

 devoid of such bodies ; almost all the species are provided with a 

 dermal membrane, which is more or less filled by foreign bodies, and 

 not a few have them also throughout the rest of their syncytium, so 

 that the whole body comes to form a compact mass of sand, traversed 

 by a few spaces of the body-cavity. 



The genus Psammasciis is tubular and monozoic ; it has the 

 closest resemblance of all the Dysideidae to the genus Spongelia, from 

 which, however, it may be distinguished by the presence of the foreign 

 bodies in its soft parts. The author finds in P. decijpiens the follow- 

 ing constituents in the foreign matter : — 



Per cent. 



Pieces of Lamellibranch shells 49 



Sand 29 



Foraminifera 11 



Sponge-spicules 9 



Parts of Echinoderms, Seleroderms, of Gorgonids, 

 Ascidians, &c 2 



100 



Similar tables are given in the course of the descriptions of the 

 species of the genus Dysidea : D. favosa, D, callosa, and D. argentea. 

 The sponges of this genus are massive and polyzoic, and there are 

 no foreign bodies in the syncytium. 



The genera Psammodema (P. ramosum), and Psammojpemma (P. 

 densum) also belong to this family. 



In the course of the descriptions, especial attention is directed to 

 the gastrovascular system, and to the arrangement of the fibres. It 

 seems to be certain that the skeleton of all sponges in which the 

 current of water passes in a regular direction, has at any rate its 

 primary fibres arranged in accordance with this direction ; and this 

 law would appear to be true whether the skeleton consists of horny 

 fibres only, or of hard structures only, or of both combined. 



An interesting observation made on an oviform Stellospongia, in 



* Zeitschr. wiss. Zool., xxxv. (1880) pp. 88-129 (3 pis. and 1 fig.). 



