4 ARTHUR DENDY. 



able paper (4) on the '^ Mode of Circulation in the Spongida," 

 in which he advocates the theory that " the particles that are 

 taken in with the water through the pores of the dermis fall 

 directly into the subdermal cavities, and pass thence into 

 the large excretory canals, from which they are afterwards 

 deflected to their destination through smaller branches, 

 whose apertures may be seen in the walls of the former/' He 

 adds, " This perhaps is best seen in Teichonella labyrin- 

 thica, wherein the chambers, which are arranged in juxtapo- 

 sition perpendicularly to the lamina of which the sponge is 

 composed, thus pass directly through it from one side to the 

 other, having therefore on one side the pores or pore-dermis, 

 and on the other the vent ; in short, exactly like those of 

 Grantia compress a, only there is no cloaca. We must, 

 however, regard this chamber as at once arapullaceous sac and 

 excretory canal ; for the pore-dermis being at one end or side 

 of the lamina and the vent at the other, the circulation passes 

 into the former and out at the latter, through the chamber, 

 where the nutritive particles are instantly taken up by the 

 spongozoa lining its cavity. Hence the holes in the walls of 

 the chamber, which are very numerous, may serve for the 

 purpose of intercommunication, where the walls of the neigh- 

 bouring chambers are in direct contact with each other, or for 

 the purpose of allowing the ova developed in the intercameral 

 tissue to pass into the chamber and thus be expelled. There- 

 fore these holes would seem to have more functions than those 

 ascribed to them in the wall of the ampullaceous sac of the so- 

 called 'siliceous sponges,' ex. gr. Spongelia avara." For 

 a further elucidation of Mr. Carter's views on the canal 

 system of sponges in general, the student is referred to his 

 paper (5) ''On the Position of the Ampullaceous Sac and the 

 Function of the Water Canal System in the Spougida;" at 

 present I wish to consider only the particular case of Grantia 

 labyrinthica. Mr. Carter's account of the arrangement of 

 the canal system in this sponge is supplemented by a figure 

 (PL IV, fig. 7), wherein the flagellated chamber (= ampulla- 

 ceous sac or radial tube) is represented as being perfectly 



