AmpuUaceous Sac in the Spongida. 209 



Lastly, in a portion of tympanizing sarcode cut out from a 

 dried fragment of Gcelongia vasiformis and placed under a 

 power of about 500 diameters, the ampuUaceous sacs in juxta- 

 position, although dry^ may be distinctly seen on the tympa- 

 nizing sarcode with their circular apertures still open in many 

 instances. 



To return, however, to the position of the ampuUaceous 

 sac in the specimen of Wilsoneila to which I have alluded, 

 there can be no doubt that when brought into view in the 

 interior of the sponge in a thin slice stained and mounted in 

 glycerine, as above mentioned, it may be seen in more or less 

 plurality and more or less approximated on the confines of the 

 smaller excretory canals, where these have been so cut across 

 as to enable the observer to look down into them. Instances 

 then present themselves where the sharply-defined globiform 

 ampuUaceous sac may be seen to rest on its side in the sub- 

 stance (plastic connective tissue &c.) of the sponge immediately 

 under the surface-membrane or epithelium of the canal with 

 its circular mouth opening on a level with the latter. 



As above stated also, the shape of the ampuUaceous sac 

 is not invariably globiform, but in no instance have I been 

 able to see any other canal in connexion with it than that of 

 the excretory system, on the surface of which the "circular 

 aperture " opens. Nor have I in any instance been able to 

 trace any canals leading directly from the pores on the surface 

 into anything but the cancello-clathrate subdermal structure, 

 within which the ampuUaceous sacs, according to my obser- 

 vation, only begin first to appear, that is in the body-substance 

 of the sponge. 



Still, it has often appeared to me that the ampuUaceous 

 sacs, when grouped together in a massive form, are fixed in 

 a kind of fibrous trama wherein they are connected with one 

 another by tubular intercommunication, which may finally 

 open upon the surface of an excretory canal. Nor have I 

 been able to see the circular aperture in any of these instances, 

 where it might have been hidden by the smallness of the ex- 

 cretory canal among the aggregated ampuUaceous sacs. In 

 short, I have never been able to see the circular aperture open- 

 ing upon the surface of the excretory canal, excepting where 

 the ampuUaceous sac has been favourably situated for this 

 purpose, as above mentioned. 



1 do not wish it to be inferred for a moment from v.'hat is 

 above stated that I discredit anything that has been published 

 by Dr. F. E. Schulze ; indeed, what he has stated with respect 

 to the incurrent and excurrent apertures of the ampuUaceous 

 sac is verified in the chamber of Teichonella labyrinthica^ 



