6QQ E. KIEKPATEICK. 



By macerating specimens in Eau de Javelle the calcareous 

 framework stands out clear (PI. 32, fig. 6, and Text-fig. 3, 

 see Section 2 b). 



Having given a general account of the external appearance 

 and coarse anatomy of Merlia, I will now describe the 

 sponge more in detail under the following headings : 



(1) The canal system. 



(2) The skeleton ; (a) siliceous, (/;) calcareous. 



(3) The soft tissues and cells. 



(4) Young stages of M e r 1 i a. 



(5) Theory of construction of the calcareous skeleton. 



(6) Systematic position of Merlia. 



(7) On some resemblances between the calcareous skeleton 

 and certain Palajozoic fossils. 



(8) Summarj'. 



(1) Thk Canal Systeji : a Xew Type. 



It would have beeu very difficult to have learned the 

 structure of the canal system from contracted specimens. 

 Under such conditions no surface openings are to be seen, 

 and the upper part of the sponge is squeezed down — like a 

 closed concertina — into the open crypts.^ Some examples of 

 this very contractile and sensitive sponge, dragged up with a 

 mass of shells and debris from sixty fathoms, were resuscitated 

 by trailing them in a bottle in the sea, and then suddenly 

 dropping them into Flemming. In these specimens not only 

 are some of the oscules and pores open, but the whole sponge 

 is expanded and shows wide ectosomal spaces. In contracted 

 specimens the sponge surface almost rests on the calcareous 

 tubercles, but in expanded examples the latter are a consider- 

 able distance below. 



The larger openings or oscules measure about 60// in 



* Open crypts — the uppermost spaces in the calcareous skeleton. In 

 the macerated skeleton these spaces are open and not roofed over by 

 tabula;. 



