8 Porifera. 



Sponginplatte with dendritically ramifying fibres ; they differ only in details of 

 little moment. The great difference lies however in the presence of free spongine 

 spicules in D. The description of A. sulfurea, A. rosea and Hulisarca dujardini 

 contains hardly anything new, and the synthetic part of the paper is almost a 

 paraphrasis of known or formerly mentioned facts. 



Delage describes the post-larval development of Aplysilla sulfurea. The anterior 

 part of the larva only seems to be naked; in fact it is ciliated by very short 

 flagella. The posterior part bears very long flagella. The central mass of the 

 larva consists of a network of cells. There is no sharp distinction between epi- 

 dermic, intermediate and amoeboid cells as in Spongitta, Esperella and Reniera, 

 mentioned above. After fixation the flagella are resorbed and move towards 

 the centrum ; the epidermic cells cover the surface. Some of the inner cells soon 

 become amoeboid and capture the originally flagellated cells. Some of the latter, 

 however, are not captured ; they then form anastomoses between each other and 

 with the amoeboid cells. They form together a syncytium, but after a short time 

 this falls to pieces; in this way are obtained petites agglomerations, formees 

 d'une seule cellule interne amoeboi'de et d'un petit lot de ciliees. The small 

 groups after 2 or 3 days form again larger groups together; meantime in the 

 former the amoeboid cell goes to the periphery. The end is that the amoeboid 

 cells become flatter, join and thus form a continuous envelope around the other 

 cells. A hole then becomes visible between these cells and thus a primitive 

 flagellated chamber is formed. Neighbouring chambers can fuse, until finally 

 elongated sacs are formed. 



Bidder ( 2 ) believes now to be able to state that his suggestion that the ecto- 

 derm cells of the horny sponges are of the same form and character as those in 

 the Homocoelaa [see, infra p 10, Bidder ('), undBericht f. 189lPorif. p 6] really is 

 true. In a sponge which fairly corresponds to Cacospongia scalar is Q.&. the author 

 found that the cells in question are of a flask-shaped form, very slender, elongated, 

 and thin-necked. They open on the surface in the centre of hexagonal areas (by 

 silver-lines) and thus not in any interstices between them. Within an area no 

 nucleus was ever visible; on the other hand it was always clearly visible in the 

 base of the pendent cell body. The spongoblasts of the primary fibres form a 

 continuous tissue with the ectoderm cells and resemble them indistinguishably. The 

 author believes that flask-shaped epithelium, as described for Leucosolenia, is not 

 only present in Cacospongia but presumably in all Porifera. The physiological 

 meaning of these cells is probably an excretory one. A comparison is added of 

 the results obtained respectively by Bidder ') and Minchin (*). 



C. Porifera calcaria. 

 See, supra p 3, Vosmaer I 1 ), p 4, Topsentp). 



I. Heterocoela. 



See, infra p 10, Bidder I 1 ). 



Dendy( 2 ) reclassifies the Heterocoela. More stress is laid upon the arrange- 

 ment of the skeleton and less upon the form and arrangement of the flagellated 



chambers, which vary considerably, even within the limits of a single species. 



Lendenfeld's group Sylleibidae, created to include the intermediate forms 

 between the Sycons and Leucons of Haeckel, seems to the author very artificial^ 

 as, according to his own observations, it appears that the transition from the 

 Sycon to the Leucon type of canal system has not taken place along a single line 



