SPONGES 



17 



off from one another 



and secondly, the degree to which the indivi- 

 duals produced in this way become 

 distinct from one another, or remain 

 fused together. 



Instances of the way in which 

 the mode of budding and the union 

 of the persons influence the form 



osc. 



Fio. 24. 

 Thenea ■murimta, Bwk., natural 

 size, r.t, root tuft; p, symbiotic 

 polyps (Palythoa). 



Sp.br 



Fio. 25. 

 Tribrachion Schmidtii, Wcltner 

 (after Sollas). sp.b, sponge body ; 

 e.t, exhalant tube. 



L.o: 



Fio. 20. 



Disyringa dissdmilis, Ridley (after SoUas). A, 

 the wliole .sponge reconstructed from fragments, 

 t.o, incurrent ai'erture; i.t, incurrent tube; sp.h, 

 sponge body ; e.t, exhalant tuV)e ; osc, osculuni. Ji, 

 diagrammatic vertical (longitudinal) section of the 

 si)oiige. a, b, c, transversi' sections at three ditferent 

 points ; a, showing the four divisions of the excur- 

 rent tube ; and b, the four divisions of the incurrent 

 tube, which at c is undivided. 



of the colony as a whole are well seen in Ascons, and especi- 

 ally in the genus Leucosolenia, where the individuals can be easily 



