252 Pr. G. C. J. Vosmaer on the 



distinctly in the Geodidse and in many Ancorinidse. Amongst 

 the Corticidge and Plakinidse a marked reduction in the multi- 

 plicity of the skeletal elements has taken place ; the latter 

 family also show clearly how triradiate spicules, nay even simple 

 styli*, may arise from quadriradiate forms. In theOligosilicina 

 the reduction of the spicules has gone still further ; Ghondrilla 

 retains only the characteristic euasters f or spherasters J. In 

 Cliondrosia and Oscarella the skeleton has completely 

 vanished ; but they have retained the characteristic granular 

 condition of the ground-substance. Oscarella is nearly related 

 to Chondrosia, and Cliondrosia to Ghondrilla. But now the 

 step from Ghondrilla to Gorticium does not appear to be very 

 greatj and so I believe in the existence of a connexion 

 between the so-called askeletal forms and the true Tetraxonina. 



In many Tetraxonina we see a kind of tendency to lose the 

 tetraxonid spicules, and we find more and more frequently the 

 long, smooth, peculiarly shining, radially disposed styli coming 

 to the fore. But the Tethyadge are forms in which this degene- 

 ration has become complete. The aj-rangement of the smooth 

 shining styli is, however, still markedly radiate ; fibres and 

 stellate s])icules are still present and also the granular ground- 

 substance. Finally, these same conditions in the Polymas- 

 tidge mark a transition to the Suberitidse. 



Turning now to the connexions of the Cornacuspongige 

 inter se, we find here the newly acquired spongin attaining 

 the first importance, while the spicules ultimately completely 

 vanish. Many Halichondrice still show a resemblance to the 

 Suberitidse ; but the arrangement of the skeleton is always 

 more irregular, i. e. less distinctly radiate ; and with this fact 

 must be connected the gradual loss of definite external form. 

 It seems to be generally agreed that there is really a close 

 relationship between the Halichondrina and the Ceratina ; 

 indeed most of the younger spongologists have repeatedly 

 brought forward new arguments in favour of this view. I 

 refer particularly to the works of von Lendenfeld § and 

 myself ||. I am therefore somewhat surprised that Sclmlze 

 should seem inclined to lay so much stress upon the entire 

 absence of siliceous spicules. 



We have thus considered somewhat more closely the rela- 

 tionships of the Sponges, and the question now arises, How can 

 one represent to one's self their connexion, i. e. their descent ? 

 From what has been said, every one may judge for himself 



* z= Stdbnadeln,^ osm. ; acuates,'!Sk, 



t " Sternchen." f " Kugelstenicheu." 



§ * Zoologisclie Anzeiger,' 1884, uo. 164. 



II jMitth. zool. Stat. Neapel, Bd. v. 1884, p. 490. 



