346 THE SPONGIDA OR PORIFERA. 



During continued and repeated observations of various species 

 of Sponge, Grant noticed that the currents invariably flowed in the 

 sauie direction through the oscula {a, a, a, a, a, Figs, i, 2, 3, 

 Plate XIV.), viz., from the interior of the sponge outwards. For 

 the purpose of avoiding all chance of error, and thinking it possible 

 that, during the close observation of a single osculum extending 

 over a lengthened period, the currents through other oscula of the 

 same sponge might be reversed and flowing towards the interior, 

 he " took from the rocks some specimens of the Spongia compressa 

 (Fig. 4, Plate XIV.), constructed like a small white paper bag, 

 with only one round aperture at the extremity of the body ; and 

 on placing each in succession under the microscope with sea-water, 

 found that each of these animals sent forth from the only aperture 

 of their bodies a slow but constant stream." 



Our specimens of this Sponge (Fig. 4, Plate XIV.), the Spongia 

 compressa of Grant, but better known now as Sycandra conipressa, 

 resemble creamy white compressed or flattened bags, or sacks, 

 slightly stalked at the base (where previously attached to sea-weed, 

 or less commonly to rocks), oval or ovate in form, usually broader 

 towards the base, and narrowing gradually up to the single rounded 

 osculum {a), which measures from a half-inch to one-third of an 

 inch in diameter. Our specimens measure about one inch across 

 at the broadest part, and from one and a quarter inches to two 

 inches in length. The large specimen is a little worm eaten. 

 More oscula than one are formed in old growths, but these natural 

 openings occur at the angles or margins. It is noticeable that, in 

 the largest sponge of the group, the lateral dimensions have not 

 increased correspondingly with the length. 



After numerous observations, having noticed that the water 

 currents invariably passed from the interior of the sponge through 

 the oscula or larger openings outwards, conveying quantities of 

 excrementitious matter. Grant suggested that these openings should 

 ho, tQrmo^d fiEcal orifices, in contradistinction to the minute apertures 

 or pores, scattered all over the surface, through which the water 

 passed into the sponge. 



The same observer pointed out that the different position of 

 the /cecal orifices, or oscula, in various specimens depended greatly 

 on the direction and manner in which the Sponges grew. Thus 



