140 Dr Grant's Observations on the Structure 



Pig. 22. Living Spongia oculata, shewing its currents, mode of 

 generation, &c. a, a, Minute pores transmitting water oblique- 

 ly into the canals. 6, h. Fecal orifices discharging currents, 

 feculent matter, and ova. c. Strong fibrous part of the animal 

 by which it hangs from rocks. 



Fig. 23. Living Spongia compressa, with a part of its side 

 , laid open, to shew the terminations of its canals in the interior 



of its general cavity. «, Expanded base by which it hangs 

 from rocks, fuci, &c. 6, Compressed terminal opening of its 

 general cavity, by which the currents, ova, and feculent matter, 

 finally escape, c, Minute pores by which the water passes 

 obliquely through its parietes. d, A part laid open, to shew 

 the fecal orifices terminating in the general cavity of the ani- 

 mal. 



Fig. 24. A pore of the Spongia panicea highly magnified, to shew 

 {a) its bounding fasciculi, and {b) a defending fasciculus spread 

 over a gelatinous network. 



Fig. 25. A pore of the Spongia papillaris highly magnified, to 

 shew («) its bounding fasciculi, {h) the part where the bound- 

 ing fasciculi cross each other to form recesses for the ova, and 

 to which the connecting matter of the spicula was supposed to 

 be confined, and (c) the most usual appearance of the gelati- 

 nous network of the pores in this species. 



Fig. 26. A transverse section of an internal canal of the Spongia 

 papillaris. «, Its bounding fasciculi, covered with the very 

 minute monade-like bodies composing the parenchymatous 

 matter, h, Groups of imperfectly formed ova lying in recesses 

 of the parenchymatous matter, c. Simplest form of the gela- > 

 tinous network found within the canals, d, Ova hanging by 

 their tapering extremity to the side of the internal canal, and 

 producing currents by the motions of the ciliae covering their 

 free surface. 



Fig. 27. Highly magnified ovum of the Spongia panicea, viewed 

 from above, when about to fix. a, Central opaque part occu- 

 pied by spicula, and covered with ciliae. h, Zone of vibrating 

 cilise distinctly seen round the margin. c, Zone of accumu- 

 . lated sediment, produced by the ciliae constantly clearing the 

 space next the ovum. 



Fig. 28. "Highly magnified ovum of the Spongia panicea, viewed 

 laterally, to shew its entire ovate form, a, Ciliae, longest on 

 the vertex of the ovum, and resting on a more translucent part 

 of the ovum, h, White pellucid base by which the ovum fixes 



