No. 3-] DEVELOPMENT OE MARI.XE SPONGES. 339 



everywhere beneath a dermal membrane. Spicules, stout 

 skeletogenous oxeas, -fJ'^ mm. long and often slightly bent ; 

 microscleres (oxeas) of varying length ; also a few tylotes. 

 Dermal membrane strewn with oxeas of full size, amongst 

 which are scattered microscleres, with here and there a tylote. 

 Membrane supported by brushes of oxeas containing a very 

 few tylotes. Spongy tissue contains radial skeletal bundles, 

 composed of oxeas, running in from the brushes ; bundles com- 

 posed of same spicules crossing the former at right angles 

 some little distance below the surface ; and numbers of oxeas 

 scattered freely through the tissue in such a way that they 

 cross one another in every direction, but are not cemented 

 together to form a network. Gelatinous tissue contains both 

 ordinary oxeas and microscleres scattered freely about, micros- 

 cleres most abundant immediately round main efferent canals. 

 Green Tm-tle Cay, Ba/tainas. 



Tedanione foetida is found in the " sounds " on the roots of 

 the mangrove. The surface of the sponge is furrowed in a 

 manner recalling the surface of Tedania, but the furrows are 

 not nearly so abundant nor conspicuous as in the latter genus. 

 On cutting the sponge open it is seen that the body is divided 

 as in Tedania into spongy and gelatinous tracts, the gelatinous 

 tissue lying around the main efferent canals. But it is only 

 occasionally that the gelatinous tissue comes to the surface. 

 In most places it lies in the interior completely covered by 

 spongy tissue. In PL XXII, Fig. 96, a vertical section through 

 the base of the sponge is shown, and it is seen that the 

 gelatinous tissue is wholly in the interior of the body. In PI. 

 XXII, Fig. 95, a transverse section through an oscular papilla 

 is shown, and here the resemblance to Tedania is greater, for 

 the gelatinous tissue comes to the surface in several places. 



The dermal membrane is strengthened by numerous oxeas 

 of full size, PL XXIII, Fig. 100, and the pores are few and 

 scattered. PL XXII, Fig. 97, represents a section vertical to 

 the surface, and shows the gross features of the canal system. 

 The subdermal cavities are numerous and open into larger or 

 smaller afferent canals, by which the water is introduced into 

 the spongy regions. The flagellated chambers communicate 



