440 



THE VOYAGE OF H.M.S. CHALLENGER. 



tinuous skeletons were perfectly cleaned and exposed to view ; also pieces from different 

 parts of the sponge were, after short treatment with hydrochloric acid and subsequent 

 washing with water and alcohol, dehydrated en masse, soaked in spirit of turpentine 

 or xylol, embedded in paraffin and .cut into sections by means of the microtome in 



KlG. 162. — Plieronema carpenteri (Wyv. Thorns.), a representative of the Hyaloneiiiatiilir. 



various directions, but principally perpendicular to the surface. Such sections, in which 

 all parts of the skeleton stood out clearly in the perfectly transparent soft parts, served 

 principally for ascertaining the situation and distribution of the separate siliceous portions 

 as well as for deciding whether the spicules which would have become separated in 

 complete maceratir.n were in their normal situation. 



