134 Dr Grant's Observations on the Structure 



this animal appears to present a new and singular mode of 

 internal gemmiparous generation. Since these germs, or so- 

 named ova, are evolved within the body of the parent, and are 

 detached without injuring or affecting its general form, this may 

 be considered as a more complicated, or more perfect, kind of 

 generation, than that by spontaneous division, exhibited by ani- 

 malcules, where the form of the parenfs body suffers materially 

 during the process, and half of its substance is removed. As 

 the ova of the sponge, however, are not fully formed individu- 

 als at the time of their separation, but require to undergo a 

 further change to bring them to the fixed and perfect state of 

 the parent, this mode of generation is less perfect than the true 

 external gemmiparous generation of the hydra, where the new 

 individual falls off from the body of the parent in a state of per- 

 fect maturity. Many other zoophytes exhibit the same kind of 

 internal gemmiparous generation by the detachment of imper- 

 fectly formed portions of their soft substance ; their ova re- 

 quire to undergo the same metamorphosis to bring them to the 

 perfect state, and they exhibit the same singular spontaneous 

 motions during the intermediate state between the time of their 

 forming a part of the parent's body, and that of their ex- 

 istence as new individuals. Mr Ellis observed similar spon- 

 taneous motions in the ova of the Campanularia dichotoma, Ca- 

 volini in those of the Gorgonia verrucosa and Caryophyllia ca- 

 lycularis, and I have observed them in those of the Plumularia 

 Jalcata (See Ed. New Phil. Journ. vol. i, p. 155). The power 

 of spontaneous motion is not given in vain to these minute por- 

 tions of gelatinous matter on which the propagation of the spe- 

 cies depends. As the fecal orifices open into the general cavi- 

 ty in such cup-like sponges as the *S'. ventilabrum and S. patera, 

 which sometimes appear to grow erect in the still recesses of the 

 deep, the spontaneous motions of the ova in these, and, in all 

 erect tubular species, will aid their escape, and prevent them 

 from destroying the parent, by a parasitic growth in the interior. 

 The power of spontaneous motion will prevent the ova of such 

 species as the S. oculata, S. panicea, S. palmata, and S. compres- 

 sa, which hang vertically from the roofs of caves, from sinking 

 by their gravity to the bottom, where they could not fail to be 

 crushed or buried among the moving sand, and will enable 



