88 AET. 1. 1. TJIMA : HEXACTINELLTDA, III. 



inconsiderable part of the periphery of this surface is reflected 

 outwards and backwards, forming at one place an ear-like flap 

 almost touching the lateral surface. The irregular gastral surface 

 is much folded and creased, which may have occurred in the desic- 

 cating process. It is covered all over with an extremely delicate 

 gastral layer, which is supported on fine hypogastral fibers barely 

 distinguishable to the naked eye. Through and close beneath the 

 layer are seen the apertures of excurrent canals. These are mi- 

 nute near the oscular rim but become larger towards the center, 

 where thev mostlv measure about 2 mm. thou2;li son e are as much 

 as 6 mm. in diameter. The larger apertures lie separated 

 from one another by a space usually narrower than their own 

 width. 



That the above considered terminal area of the sponge is the 

 gastral surface, is placed beyond the reach of doubt by the fact 

 ascertained by direct observation, that the chamber layer beneath 

 it has the apopyles turned towards that surface. 



The oscular edge is sharp, though not thin. No prostalia 

 maro-inalia are seen alono; it. 



The kiteral surflice of the sponge-body shows a dermal skeleton 

 of exquisite beauty. The dermal layer is exceedingly fine and 

 delicate ; its minute meshes are just discernible as such with the 

 naked eye. It is borne on two sets of hypodermal latticework. 

 Of these one is formed by the paratangentials of pentactinic 

 hypodermalia (PI. YIL, fig. 19). This is quite delicate, present- 

 ing small meshes which are generally regularly rectangular and 

 measure onl}" about half a millimeter in the length of sides. The 

 other hypodermal latticework is formed of fibrous bundles of 

 varying caliber. It is the coarsely and irregularly meshed lattice- 

 work that is prominently visible in fig. 1, PI, YII. In somç 



