THE BKITlijH SPONGES. 19 



them, that they cannot be considered to be the ordinary 

 media of the propagation of sponges in general. Their very 

 position in the scale of organized beings, — vacillating be- 

 tween the lowest members of the two kingdoms, — forbids us 

 to believe that sponges could be oviparous ; and, consistent- 

 ly with this theoretical deduction, in by far the greater num- 

 ber which I have examined, there has been no appreciable 

 difference in the composition or texture of the species at 

 whatever season, or at whatever stage of its growth, the ex- 

 amination has been made. Thus I have been led to con- 

 clude that sponges are propagated by self-division, — by de- 

 taching at irregular intervals, and in the form of sporules, 

 scarcely regulated by seasons, small portions of their mass 

 or gelatine, which, carried abroad by tides and other influ- 

 ences, fall into favourable situations, and gradually there 

 develope, until they assume the form and texture of their 

 originals.* 



Sponges inhabit every sea and shore. According to La- 

 mouroux they are very abundant and various between the 

 tropics, but become less so in temperate latitudes, and con- 

 tinue to diminish in number, in variety, and in size as we 

 trace them into European and colder seas, until they al- 

 most disappear in the vicinity of the polar circles. The 

 branched sponges with a compact feltred tissue are more 

 common than others in the seas of cold regions, where the 

 species of a loose textm-e, which grow in large massive 

 forms, either do not exist or are very rare. In this order of 

 distribution sponges agree with other zoophytes, and seem 



' The fibre of a dried si)onge is frequently coated with a " rugous 

 film, containing minute granulations" Mr Bowerbank considers these 

 granulations to be the incipient gemmules of the sponge — Microsc. 

 Journ. i. p 9. I believe tbein to be the matured gemmules or sporules. 



