130 ANATOMY AND PHYSIOLOGY 



from the appearances manifested at the oscular orifices at 

 the inner surface of the sponge ; a more detailed account 

 of these investigations is published in the 'Transactions of the 

 Microscopical Society of London,' vol. iii, p. 1 37 . Pig. 312, 

 Plate XXI, represents a longitudinal section of the inter- 

 marginal cavities of Grantia compressa with the ciUa in 

 situ. Kg. 313, a view of the small portion of the inner 

 surface of the sponge, exhibiting the oscular orifices and the 

 appearance of the cilia in motion within them, and detached 

 cilia and cells from the same sponge. 



In the course of my endeavours to detect the ciha in 

 Halichondroid sponges, I have frequently observed in slices 

 of the sponge taken from the surface, that the incurrent 

 action has continued for a considerable period, while in 

 sections of the same sponge taken from deep amid the 

 tissues, no such action of the currents could be detected. 

 In sections from the surface in which the inhaling process 

 was in vigorous condition, when the inside of the section 

 was examined, that peculiar flickering appearance was often 

 visible in the cavities immediately beneath the dermal 

 membrane, which is so characteristic of minute cilia in 

 very rapid motion; and although many molecules were 

 rushing inward with considerable velocity, others might be 

 seen which continually waved from side to side but made 

 no progress forward ; in fact they presented precisely the 

 appearance that I have described as taking place in the 

 oscula of the proximal ends of the great intermarginal cells 

 of Grantia compressa ; and I have no doubt, in my own 

 mind, that those of the Halichondroid sponges were also 

 extraneous particles of matter adhering' to the apices of the 

 minute cilia, rendering their motions apparent, while the 

 cilia themselves were perfectly invisible. 



Carter, in his paper on " Zoosperms in Spongilla" 

 published in the ' Annals and Mag. Nat. Hist.,' vol. xiv, 

 Second series, p. 334, describes ciliated bodies from a 

 Sponffilla from the water-tanks of Bombay, somewhat 

 similar to those of Grantia compressa, but the basal cell 

 appears to be larger and the cilium shorter in their pro- 

 portions than those of G. compressa. The author, in 



