22 Mr. H. J. Carter on the Anatomy 



a distinct cell-wall) is circular and evidently sphinctral, inas- 

 much as it has the power of dilating and contracting itself, 

 while, by adjusting the focus of the microscope to the interior, 

 when the aperture is open, in situ, under water, and in an 

 active living condition, cilia may be observed in a state of 

 undular vibration. 



Thus, watching the particles of carmine as they pass from 

 the water through the pores, they appear to reach the interior 

 of the ampullaceous sac through the opening just described. 

 And still keeping our eye on the sac, we may observe 

 that, after a time, certain of the coloured particles are trans- 

 ferred en masse into a circumjacent branch of the excretory 

 canal-system, whence they immediately get into the main 

 trunk, and are ejected at the vent ; so that it must be assumed 

 (for it has not been demonstrated) that there is a second or 

 excremental aperture in the sac here, as in that of the 

 calcareous sponges, unless the material is extruded into 

 the excretory canal through an extemporized aperture, after 

 the manner of an Amoeba. The ampullaceous sac in the 

 siliceous sponges is, for the most part, globular, but may be 

 subglobular and sac-like of different shapes. In diameter it 

 is about 1 -600th of an inch in the siliceous sponges, and the 

 body of the spongozoon (about to be described) from l-6000th 

 to 1 -3000th of an inch in diameter, both ampullaceous sacs 

 and spongozoa being by far the largest in the calcareous 

 sponges. 



Sponyozoa. 



So far our observation has been limited to what takes place 

 in the ampullaceous sac generally. We have now to see what 

 the organs in the sac are that receive the colouring-matter ; and 

 to ascertain this we have only to tear up a portion of the thus 

 coloured sponge with needles, when we shall observe that the 

 particles of carmine are in monociliated conical bodies, which 

 in juxtaposition form a pavement-like structure round the inner 

 surface of the sac, from which their cilia vibrate into its in- 

 terior. For these bodies singly I have proposed the name of 

 "spongozoon " ('Annals,' 1872, vol. x. p. 45). 



Moreover we observe that in the active living state, or just 

 after the spongozoon has been scratched out from the body of 

 the sponge (for it soon passes into an amorphous amoeboid 

 condition), the spongozoon has a definite form, as the late 

 Prof. James-Clark, of America, first pointed out in the calca- 

 reous sponge called Leucosolcnia botryoides ; and in another cal- 

 careous sponge, viz. Grantia compressa, I find it to consist ot 

 a round or conical body, from which projects a long bacilliform 



