REPORT ON THE HEXACTINELLIDA. 



41 



very closely related forms, perhaps even referable to the same genus, one of which occurs 

 on soft ground, and possesses a completely developed root-tuft, while the other, which 



Dlcfyonalia. 



Fig. 2. — Diagram of the arrangement of the Spicules. 



grows on a firm substratum, exhibits no trace of such a structure. It is, indeed, readily 

 conceivable that one and the same species might, in different circumstances, produce a 

 root-tuft or not. 



(ZOOL. CHALL. EXP. — PART LIU. — 188G.) 



Ggg6 



