OBSERVATIONS OX THE Eui^LECTÉtLTDi: GENERALLY. lÖ 



the small hexactinose and the larger spherical discohexasters, 

 both of exactly the same characters as those of the body. The 

 former are common everywhere, while the latter have been found 

 scattered here and there in the stalk only. 



The large excurrent canal in the stalk is likewise lined with 

 a tliin layer of fine diactinic parenchymalia, free of synapticular 

 formations. No special canalaria exist here, but the hexasters 

 are represented by the usual, small, hexactinose discohexaster and 

 the hexactinose codonhexaster of a larger size — the former in 

 excessive abundance ])ut the latter only sparsely. It may be 

 pointed out that the presence of the codonhexasters along the 

 canalar wall manifests a point of agreement, and indicates a 

 direct continuity, between the surfaces of that canal and oi' the 

 gastral cavity, in a manner as it is perfectly natural to find, as 

 we did, the same spherical discohexaster under the conthuious 

 dermal surfaces of the stalk and of the back of the sponge-body. 



Ohset'cations on the l^JuplecfeUidw yenefally* 



As to the systematic position of Placosoma paracUctyum, it 

 is safe to say that it should be 2)laced under the Euplectellidic. 

 In an attempt to determine, as nearly as possible, its position 

 within that family, I have been led tu undertake a renewed study 

 of all the membejs of the family as regards their known systematic 

 characters, and this induces me to make here some observations 

 concerning the family diagnosis and the division into subfamilies, 

 and in this connection I take the opportunity to modify certain 



