530 



REVISION OP THE AXIXRLLIP^., 11., 



They run with slight divergence (gradually becoming more 

 nearly parallel to each other as they proceed), and with occa- 

 sional branching, generally at a distance of from 200 to over 



300/A apart, to meet the surface 

 almost at right angles. As the 

 surface is approached, their spicules 

 increase in number and become dis- 

 posed for the most part in a some 

 what plumose manner, the fibre un 

 dergoing a gradual change in char- 

 acter culminating in the formation, 

 at its extremity, of a corymbifoim, 

 slightly divergent tuft consisting 

 frequently of as many as 10 or 12 

 spicules. Elsewhere in the radial 

 fibres the spicules lie mostly with 

 their long axis in, or only very 

 slightly inclined to, the direction of 

 the fibre ; but obliquely directed 

 spicules, disposed more or less in an 

 echinating fashion, are by no means 

 uncommon. Some of the latter 

 become united at their apices, by 

 means of spongin, with adjoining 

 fibres, and thus assist in the task 

 performed by the connecting fibres; 

 occasionally such spicules are en- 

 sheathed with spongin. Tlie con- 

 necting fibres proper, of which men- 

 tion has been made abv.ve, are 

 formed entirely of spongin, like 

 those of the axial region; they are 

 very slender, varying in stoutness 

 from less than o/i to at most 20 or 

 2r)/x, and occur at distances apart usually exceeding, say, 300/i; 

 where occurring clo.sely together, they generally interunite among 

 themselves. 



Text-fig. 13. 

 Siymaxinella dendroides. 

 a, megascleres; h, c, larger and 

 smallei' signiata. 



