374 



Dr. O. Hamann on the Phylogeny 



in septa which are extended in the radial schizocoele-cavities 

 and the latter themselves ; both structures are schizocoele- 

 structures, and originate as spaces and cavities in the con- 

 nective substance. To this must be added that the young 

 Asterias of perhaps a centimetre in diameter has no cavities 

 in its septa of the ventral surface, but that in this case the 

 longitudinal canals (periheemal cavities) must rather function 

 as sanguiferous spaces. In future, when we speak of the 

 blood-lacunar system in the Echinodermata it will no longer 

 do to characterize as blood-vessels one set of structures in one 

 group and another in another, but it will have to be shown 

 how sometimes one and sometimes another part of the schizo- 

 coele-structures conveys the true blood-fluid and stands con- 

 nected with the intestinal lacunse. 



We have therefore before us two different schizocoele-struc- 

 tures, two contrary systems, at first (Asterida) separated from 

 one another, but which may afterwards partially communi- 

 cate. The following table gives a summary representation 

 of these schizocoele-structures : — 



< 



