SPONGES 







Vic. (IS. 



Ileteroivffma Hf)f?«.«/orrfi/, Pol., part of a iransvcrse spction. The external surface is upper- 

 most ; tlie pastral surface towards tlie lower side ; the spicules are represented by straipht 

 continuous lines ; the Hat epithelium by (lotted lines ; the collar cells by numerous small circles 

 rendering the branching; nidial tubes dark. (After Pol^jaefJ", Challenger Reports.)' 'xCO. 



The leuconoid tj'pe of canal system has probably been evolved 

 from the syconoid tyjie in more ways than one. There are at least 

 two modes of evolution wiiich can be indicated with tolerable 



-Xvi>^ 





r 



Fio. 09. 



Ule argentcn, Pol., jmrtofa transverse .section. The concentric circles indicate transverse 

 sections of spicules, lyinj; within the cortex. For otlicr points see description of last figure. 

 (Al'.i-r I'lihiaell, chnll,,,,,,,- Heports.) xlOO. 



