8 OCEAN LIFE. 



number of nucleated granules ; these angular cells are laid at right 

 angles to the long axis of the Sponge, extending from the outer 

 surface to the inner, and they are crossed near the middle by a 

 thin partition, perforated in the centre. In this perforation, 

 several long, whip-like cilia were seen lashing with energy, and 

 the same organs were afterwards found to be connected with the 

 granules of which the cell walls were composed. By means of the 

 waving of these cilia, then, the water is made to flow through the 

 cells from without, being discharged into the interior of the sack 

 and poured out in streams through the oscula or openings which 

 terminate the angles of the Sponge." 



This experiment, we think, leaves no doubt of the animal na- 

 ture of Sponge. " If a Sponge be mechanically divided into 

 several pieces, every portion becomes a distinct animal. The 

 multiplication of Sponges, however, is effected in another man- 

 ner, which is the ordinary mode of their reproduction, and forms 

 a very interesting portion of their history. At certain seasons 

 of the year, if a living Sponge be cut to pieces, the channels in 

 its interior are found to have their walls studded with yellowish 

 gelatinous granules, developed in the paranchymatous tissue; 

 these granules are the germs or gemmules from which a future 

 race will spring ; they seem to be formed indifferently in all parts 

 of the mass, sprouting, as it were, from the albuminous crust that 

 coats the skeleton, without the appearance of any organs espe- 

 cially appropriated to their development. 



As they increase in size they are found to project more and 

 more into the canals ramifying through the Sponge, and to be 

 provided with an apparatus of locomotion, of a description such 

 as we shall frequently have occasion to mention. 



The gemmule assumes an ovoid form, and a large portion of 

 its surface becomes covered with innumerable vibrating hairs, or 

 cilia, as they are denominated ; these are of inconceivable mi- 

 nuteness, yet individually capable of exercising rapid movements, 

 whereby they produce currents in the surrounding fluid. As 

 soon, therefore, as a gemmule becomes sufficiently mature, it be- 

 comes detached from the nidus where it was formed, and, being 

 whirled along by the issuing streams, is expelled through the 

 fecal orifices of the parent, and escapes into the water around. 



