32 I. IJIMA : HEXACTINELLTDA. I. 



Methods used in the Studies. 



Unless intended for histological investigations, specimens were 

 simply thrown into alcohol — which was changed after a while — 

 and then permanently preserved in 70^^ alcohol, as far as was 

 practicable. Such specimens also gave the best results when 

 afterwards dried. Those which seemed not worth putting into 

 alcohol or could not be so prepared, were soaked in plenty of 

 fresh- water for several hours or overnight, during which inter- 

 val the water was changed now and then ; they were then 

 dried as quickly as possible. When imperfectly ' desalted,' 

 dried specimens are apt to absorb moisture and become soft and 

 dirty after a time ; in such cases the proper firmness may be 

 restored by again immersing in fresh-water and desiccating as 

 before. 



For the study of spiculation it was found quite important 

 in the first place to make preparations of the dermal and the 

 gastral layer and of a piece of the parenchymal septum, all to 

 be removed in such a w^ay as not to disturb in the least the 

 relative position of individual spicules. The pieces may conveni- 

 ently be mounted in Canada-balsam under the same cover-glass. 

 For a detailed study sections of the body-wall, better unstained 

 than stained and cut from a piece imbedded in parafiî^ine, were 

 invaluable. Certain points in the spiculation can only be deter- 

 mined in this way. 



The spicules may be cleaned of the crusts of soft parts by 

 boiling in sulphuric or hydrochloric acid. They are then to 

 be examined in water or after mounting in Canada-balsam. 

 The axial cross and filaments in even the finest hexasters are 



