CHAUNOPLECTELLA CAVERNOSA. 57 



leads one to the supposition that its growth takes place with 

 eonsiderahle — so to say, precocious — activity in the early period 

 of post-larval life. Later, the rate of its gT0\Yth seems to more 

 closely coincide with that of the body, so that the early ratio in 

 size of the two parts is not maintained in after-life. 



The external sur&ce of the sponge is rather uneven. The 

 dermal layer covering it is of a somewhat unusual spicular 

 composition. As seen under a hand-lens, it consists of irregularly 

 interlaced beams, running in quite indefinite directions in the 

 plane of the surface (PI. IV., fig. 7). The beams, though thin 

 on the whole, are of various degrees of strength, the strongest 

 being as much as i mm. in thickness. The thinnest beam con- 

 sists of no more than a single spicular ray, while others are made 

 up of a varying number of rays grouped together into a more or 

 less compact-looking bundle. Xot infrequently, a beam, springing 

 out from another as a branch, is seen to terminate freely, without 

 reaching up to that towards which it is directed. Altogether the 

 dermal latticework is irregular. The meshes often have sides of 

 1 mm. and more in length, and must be said to be on the whole 

 coarse, besides being irregular in shape. — The meshes are covered 

 with a sieve-like dermal membrane, made up of membranously 

 flattened trabeculœ around and between the closely disposed, 

 roundish pores (PI. IV., fig. 7). 



The want of regularity in the arrangement of dermal spicules 

 and the coarseness of the meshes serve as a convenient mark of 

 distinction between this species and certain Rossellids of a 

 bewilderingly similar external appearance, e. g., Staurocalyptus 

 glaber Ij. 



On the surface of the stalk-like base, the dermal laver is 



