On the Mode of Circulation in the Spongida. 117 



Fig. 4. Haliohondria scabida, outline of the specimen and its spiculation &c. 

 a, outline of the specimen ; b b, pore-areas ; c, part of the dermis 

 without pore-areas ; d, skeletal spicule ; e, subskeletal spicule ; 

 f, still smaller form; g, large form of equianch orate; h, small 

 form of the same ; i, more magnified view of large form, to show 

 the teeth, arms, or flukes, as they have been called, of the 

 extremities ; k, pore-areas magnified four diameters ; /, rim ; 

 m, pores ; n, still more magnified view of the pores in a fragment 

 of the sarcode charged with the small form of anchorate (Ji) ; 

 o, pores ; p, sarcode charged with the anchorate. 



Fig. 5. The same. Diagram to show the direct connexion of the pore- 

 areas with the excretory canal, a, pore-areas ; b, subdermal 

 cavities or structure ; c, excretory canal ; d, circular folds, more 

 or less extending round the surface of the excretory canal ; 

 e, apertures of the smaller branches in this canal ; /, filament 

 introduced to show the direct communication of the pore-areas 

 with the excretory canal ; g, vent, with arrow showing the direc- 

 tion of the current. 



Fig. 6. Acanthella cactifonnis, spiculation of. a, acuate form ; b, acerate 

 form. 



Fig. 7. See explanation in connexion with the paper which it illus- 

 trates, p. 122. 



XI. — Mode of Circulation in the Spongida. 

 By H. J. Carter, F.R.S. &c. 



[Plate IV. figs. 5, a-g, and 7 , a-p.~\ 



In the month of July 1857, when my observations " On the 

 Ultimate Structure of Spongilla " were published (' Annals/ 

 vol. xx. p. 21, pi. i.), I thought there could be no doubt about 

 the course of the circulation in the Spongida, as the minute 

 portion of Spongilla developed from the statoblast (gem mule 

 or seed-like body) is so small and yet so perfect that it can be 

 easily kept under the microscope, while the red particles of 

 carmine-paint that may be brought into contact with it are 

 taken in and discharged before the eye. By being " so per- 

 fect," I mean that it consists of only one "person " (Hackel), 

 that is, it is a minute epitome of sponge-structure in which 

 there is only one vent and therefore only one excretory canal- 

 system ; hence a view of the whole portion which is trans- 

 lucent can be easily commanded by the aid of a microscopic 

 power of 250-300 diameters (in water of course) . 



Under such circumstances (I must here revert to my 

 original nomenclature and diagram, op. et loc. cit. pi. i. fig. 1) 

 the particles of carmine-paint may be seen to pass through the 

 holes of the " investing membrane " (pore-derm is) into the 

 so-called "cavity " of this membrane (subdermal cavities), and 



