B. Porifera incalcaria. 2. Cornacuspongiae. 5 



D. Pseudotetraxonina. 

 See Giard. 



E. Clavulina. 



See supra, p 2, Hanitsch, p 3, Topsent ( 1 , 2 ). According to Dendy( 1 ), the co- 

 lour of Suberites wilsoni is a very powerful dye ; it is retained in alcohol speci- 

 mens and after drying. 



2. Cornacuspongiae. 



A. Halichondrina. 



See Giard. 



Dendy ( 3 ) describes several species of Chalinine spouges. They are especially 

 interesting from two points of view: 1 they afford excellent illustrations of 

 the great variability in external form to which species of sponges living in shallow, 

 or comparatively shallow, water are subjects; and 2 they illustrate in a very 

 striking way the manner in which the siliceous spicules gradually degenerate and 

 ultimately completely vanish as the horny skeleton becomes more and more 

 strongly developed . There is a close relation between Siphonochalina and Sjrino- 

 sella; perhaps they are identical. 



Topsent ( 2 ) treats of the synonymy of species belonging to Dictyocylindrus and 

 Raspailia. He accepts five species of R., the synonyms of which are given. 



Maas made accurate researches on the development of Spongilla. His paper 

 is the full account of the preliminary one from 1889 [cf. Bericht f. 1889 Porifera 

 p 5]. The results are: The ovum, which is full of yolk, developes into a solid 

 morula. On one pole of this morula appears a depression, which becomes deeper, 

 and which then is closed, so as to form a cavity. The morula is transformed into 

 a larva in which three layers may be distinguished. The outer layer consists of 

 flagellated cells. The cavity is lined by flat epithelium and gives off canals which 

 communicate with flagellated chambers. The third (middle) layer consists of yolk- 

 cells and connective tissue with silicoblasts. The fixation occurs at the pole where 

 the cavity is; the larva now becomes more and more flat. At the same time the 

 ectoderm flattens; the cells of the border become amoeboid. As soon as by this 

 flattening of the larva the flagellated chambers come nearer to the wall , the ex- 

 ternal epithelium turns inward and gives rise to incurrent canals. The primitive 

 cavity opens secondarily into the water, and thus excurrent canals are formed. 

 Subdermal cavities are formed later, in the subsequent growth of the sponge. 



Beyerinck made experiments with the Zoochlorellae of Spongilla fluviatilis, 

 but could not develope them freely. He found gemmules with Chlorella and thus 

 he suggests that a direct infection during life-time of the sponge must take place. 

 The symbiosis between Spongilla and Algae is not yet at the high point occurring 

 e. g. between Hydra and Algae. 



Weber & Weber-van Bosse describe some old and new cases of sponges in 

 which Algae grow. There is symbiosis (s.s.) in the following cases : Halichon- 

 dria spec, and Struvea delicatula; Reniera fibulata and Marchesettia ; id. and 

 Spongocladia vaucheriaeformis ; ? Spongelia pallescens and Oscillaria spongeliae ; 

 ? Psammoclema ramosum and id. ; ? Spongelia pallescens and Callithamnion membra- 

 naceum; ? Spongelia spinifera and id. ; ? Aplysilla sulfurea and id. ; ? Spongia otahetica 

 and Scytonema. (In the forms with a?, it is dubious whether there is true sym- 

 biosis or parasitism.) There is parasitism in the following cases: Reniera 

 fibulata and Thamnoclonium flabelliforme ; Dactylochalina australis and a species 

 of the Florideae (Ldfd.) ; Ephydatiafluviatilis and Trentepohlia spongophila. 



