436 Mr. H. J. Carter on the 



Arrvpullaceous Sacs and Spongozoa. 

 (Hackel's "Gastrula" when developed in situ ?) 



In the ' Annals ' of 1857, vol. xx. p. 21, I published a 

 description of the "Ultimate Structure of Spongilla^'' which 

 appears to me, so far, to be tjqjical of every other sponge, 

 both marine and freshwater, that I have examined. 



It was there that I first described and figured the " ampul- 

 laceous sac," after having fed the /S):)o?i_5r«7/a with carmine, and 

 showed that this sac was composed of a pavement -layer of 

 . monociliated cells (spongozoa) with a distinct and common 

 aperture ; also that each spongozoon took in fragments of car- 

 mine, while its cilium might be seen to vibrate in the cavity 

 of the ampullaceous sac (/. c. pi. 1. fig. 5, &c.). The terms 

 " sac " and " cell " involve the idea of a sac- and cell- wall 

 respectively, which here must be maintained on inference 

 rather than demonsti-ation. There must be a " vanishing-point " 

 in early development ; and to assume that a tissue cannot 

 exist in such a subtile state as not to be appreciable by our 

 senses, seems to me to be an untenable position. In this sense, 

 therefore, I use the terms " sac " and " cell " for these sarcodal 

 bodies respectively. 



At p. 28 (?. c.) it is stated (with reference to the undigested 

 portions) that, " after a certain time, the particles of carmine 

 which have accumulated round the inner surface of the sac 

 are gradually thrown off from its circumference, and faUing 

 into the efferent system of canals, are thus carried away and 

 finally ejected." It will be for us to consider, by-and-by, 

 whether this takes place through the pavement-layer of the 

 spongozoa generally^ or at one particular point of the sac. 



Lastly, in the ' Annals ' of 1873, vol. xii., in my paper 

 on the Grummineffi, it is stated at p. 27 : — " I cannot help 

 thinking that there are more species than Halisarca Du- 

 jardinii to be found on our coasts ; so I hope to meet with not 

 only this, but other species of the family here in a living state, 

 through which I may, by experiment, be able to add some- 

 thing more satisfactory to our knowledge of their intimate 

 structure than we at present possess." 



My anticipation in this respect will have been seen to have 

 been realized in the discovery of Halisarca Dujardinii and 

 H. lohularis on this coast ; while it so happens that by having 

 fed the latter with indigo, still more precise information of 

 the nature of the ampullaceous sac has been obtained. 



By the above description of H. lohularis it will also have 

 been seen that the ampullaceous sac is not only rendered 

 more distinct by the presence of the indigo in the spongozoa, 



