BRITISH SPONGIAD^. 371 



tions as those of the dermal membrane were observed. 

 Occasionally, for a very small space, the spicula within the 

 dermal fibre were slightly increased in length, and their 

 diameters became double those of the neighbouring ones of 

 the normal form ; and the transition from the one form to 

 the other was not gradational, but the spiculum next to 

 one of the stout ones was completely in unison with the 

 proportions of those of the general mass of the rest of the 

 dermal reticulations, and of the skeleton ; this singular 

 variation in their proportions did not appear to exist to any 

 great extent, as, on dissolving separate portions of the sponge 

 in nitric acid, but very few of the larger forms were to be 

 seen, in comparison with the number of those of the nor- 

 mal one. In one of the pieces thus dissolved very few 

 extraneous forms of spicula appeared, while in another 

 piece, treated in a similar manner, numerous extraneous 

 forms made their appearance ; these were apparently due 

 to their adhesion to the dermal portions of the part of the 

 sponge thus treated, as I could not detect such extraneous 

 forms within sections of the sponge, nor on slices taken 

 from the surface of it. The diameters of the keratose 

 fibres of the skeleton are nearly equable throughout its 

 structure, and they appear greatly to exceed the propor- 

 tions necessary to the envelopment of the single series of 

 very slender spicula that forms its axis. I found but a very 

 faint trace of the interstitial membranes, but the little there 

 was had a few tension spicula upon its surface in some of 

 the areas. 



The length of a full-sized spiculum of the normal form 

 is gigth inch, and the diameter ^^^th inch. 



I have dedicated this species to the memory of the late 

 Dr. Fleming, as a small token of respect, and in acknow- 

 ledgment of the valuable services he has rendered to zoolo- 

 gical science. 



