2 Porifera. 



Zalacostas, Pierre, Recherches sur la constitution de la spongine. in: Compt. Rend. Torne 

 107 p 252254. [7] 



A. General Works. 



See Grieg, Lang, Lo Bianco, Dunikowski. 



For the phylogeny of the whole group see Sollas (', 2 ), infra, p 5. 



Independently from Sollas [see infra, p 4], Bidder finds in Leuconia aspera, 

 fed with carmine, that the collars unite, so as to interpose a continuous membrane 

 between the afferent and efferent systems. He believes this to be a mechanism 

 for filtering the food from the water. The carmine granules are taken in 

 freely by the collared cells, not appearing in the mesoderm, and only very little 

 in the other epithelia. Primitively the collared cells both ingest and digest for 

 the sponge; the function of digestion being in some sponges, but not in L., passed 

 to cells situated in the mesoderm. The flow of water is slowest in the flagellated 

 chambers ; for this reason the function of ingestion is localized there, as well as 

 the motor apparatus, since the flagella have their highest efficiency where the 

 velocity is least". 



Neumayr gives a review of our spongiological knowledge. He compares re- 

 cent with fossil forms and tries to find out their genealogical relation. From 

 the palaeontological point of view, Tetractinellids descend from Tetracladine 

 Lithistids. Palaeozoic Hexactinellids show more irregularities in their skeleton, 

 than those of more recent date. Hence he believes, that the regular Hexactinel- 

 lids are younger and descend from the irregular ones. This view opens the way 

 to the possibility that Hexactinellids and Tetractinellids are derived from one and 

 the same stem. 



B. Porifera incalcaria. 



The material of flints has been derived chiefly from the siliceous remains of 

 sponges. Sollas ( 3 ) has now weighed several recent sponges and their mass of 

 silica, compared to the weight of flints. We may say that it would on an average 

 require 8-18 sponges to produce sufficient silica to make a flint of the size of one 

 of them. Supposing that siliceous sponges in general take the same time to grow 

 out as the bath sponge, i. e. on an average 6 years, a bed of flints would be 

 formed in less than half a century. 



See also Sollas (*, 2 ), infra, p 5, and Priest. 



I. Hyalospongiae. 



See Neumayr, supra, and Sollas (', 2 ), infra, p 5. 



II. Spicnlispongiae. 

 A. Lithistina. 



See Sollas i 1 , 2 ), infra, p 5. For Porosphaera see infra, Coelent. p 32, Ni- 

 cholson. 



B. Tetraxonina. 



See Neumayr, supra. 



According to Sollas (*, 2 ) we may trace all non-calcareous Sponges to a 

 primitive ancestor , which is called Rhagon, like the calcareous Sponges 

 were traced by Haeckel to the Olynthus. The Khagon however is only known in 

 a transitory larval stage. It has the form of a more or less hemispherical sac, the 



