858 



SPONGES AND ZOOPHYTES 



pin or may cany three or more diverging points which sometimes 

 curve back so as to form hooks. When the spicules project from the 

 horny framework they are usually somewhat conical in form, and 

 their surface is often beset with little spines arranged at regular inter - 



M 



-nic. 



FIG. 654. A, section through PhaJcellia ventilabrutii, var. connexida-, taken at right 

 angles to the surface, to show the arrangement of the parts of a sponge : p, pores 

 on the surface leading to z'e, the inhalant canals, then to the flagellated chambers, 

 fc, and thence to the exhalant canals, ec, to o, the oscula in the dermal membrane. 

 dm. B, more highly magnified view of the internal portion (choanosome) of 

 Axinella paradoxa x 290 : me, so-called mesodermal cells. Other letters as in A. 

 (After Kidley and Dendy.) 



