OF THE NATURE OF SPONGES. 



(A 



one-fiftieth to one-eightieth in breadth : others are nodose 

 either in the middle or at the extremity ; others present 

 sudden bends or lateral branches ; and there is a very 

 small kind of spicula which is remarkable fi-om the nume- 

 rous spinules with which the surface is roughened. 



Dujardin has examined ^ith great minuteness the natm*e 

 of the gelatinous matter that fills more or less the inter- 

 stices of the sponge. By teai'ing up a specimen in water 

 this glutinous substance is set fi'ee and diffused in globules. 

 These, when examined through a good microscope, arc 

 seen to change their forms gradually, so that they present 

 themselves to the beholder under twenty different phases if 

 he will allow a few minutes interval between the di'awings 

 of his designs. The globules move also across the stage of 

 the microscope by emitting various lobes and expansions, 

 with whose emission their locomotion appears to be con- 

 nected ; and sometimes they are moved by the agitation of 

 some very long filaments of extreme fineness and tenuity, 

 proceeding from their sides or extremities. (Fig. 9.) 



Fiff. 9. 



