478 EIOHARD EVANS. 



directly with the wide exhalant cauals, and occupying nearly 

 a fourth of the surface of the otherwise almost spherical 

 flagellated chamber, which is lined by collar-cells with nuclei 

 situated at their bases. The canals of the exhalant system 

 are much wider than those of the inhalant, and, as a rule, occupy 

 a central position between the fibres. As they pass down into 

 the deeper parts of the sponge they converge and unite together, 

 forming wider canals, which are few in number, and which 

 open into the somewhat spacious gastral cavity, which commu- 

 nicates with the exterior by way of an osculum situated at the 

 summit of each of the mound-like elevations of the surface. 



(4) The Gemmule. — The gemmules, which are few in 

 number and scattered about singly, are spherical in shape and 

 small in size, measuring only *35 mm. in diameter. They 

 possess a thin coat, which is not surrounded by spicules 

 specially characteristic of the gemmule, but by the ordinary 

 skeleton spicules. Their cellular contents present the same 

 characters as do those of the common species of Spongilla, and 

 each individual cell is full of the two kinds of granules which 

 are quite characteristic of the cells of Spongillid gemmules. It 

 is just possible that had the material been preserved later in 

 the year the gemmules would have been more numerous, though 

 there would appear to be no absolute necessity for the produc- 

 tion of gemmules, since the sponge lives at a depth of 300 

 fathoms, and cannot possibly be either dried or frozen. 



III. The Affinities of Spongilla moobei. 



The presence of the gemmule is the most important character 

 tending to fix the position of Spongilla moorei among the 

 Spongillidse. Gemmules have been described in marine sponges, 

 and this fact diminishes the importance of the existence of gem- 

 mules in a newly discovered sponge as a character supposed to be 

 distinctive of the Spongillidse (Topsent [12]). It appears that 

 there is no special feature in the structure of the skeleton of 

 Spongilla moorei that would cause it to be separated from 

 the Chalinidse had it been a marine sponge. It most decidedly 



