On the AmjmUaceous Sac in the Spongida. 203 



XXVII. — On the Position of the Ampullaceous Sac and the 

 Function of the Water Canal-system in the Spongida. By 

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



What we want to know in the class of Sponges, after their 

 specific description, is a general conception of the manner in 

 which the different parts of which thej are composed are 

 deveh^ped, and the way in which their vital functions are 

 performed. In the first instance a useful classification is 

 needed, by which the species may be easily determined : 

 this is the department of the naturalist, and, as a matter of 

 course, precedes all others. The second and third points 

 come under the domain of the physiologist, and here the 

 general plan of development and that of the general way iu 

 which the vital forces are maintained (excepting, for a time, 

 their peculiarities) is the primary desideratum. But although 

 the first is a sine qua non to the latter, it leads to nothing but 

 a collection of curiosities so long as the physiological part 

 remains unknown. 



Of course there is much yet to Be discovered in the study 

 of a subject so comparatively young as that of spongology, 

 and it is only by numerous contributions arising from a special 

 study of particular parts that this can ever be advanced, and 

 therefore, however restricted the inquiry may be, so long as it 

 tends to elucidate any particular point, the result must be 

 considered acceptable. In the present instance it is the posi- 

 tion of the ampullaceous sac in relation to the water-courses 

 or canalicular structure of the sponge to which I wish to direct 

 attention. 



The ampullaceous sac (" Geisselkammer " of the Germans) 

 is for the most part spherical in form, consisting of a hollow, 

 thin, transparent sphere of plastic sarcode whose wall is 

 charged with spongozoa (" Geisselzellen " of the Germans), 

 arranged tesserately, that is side by side, or in juxtaposition ; 

 the spheroidal form being truncated or cut off, that is absent 

 at one part, whereby a sharply defined circular aperture is 

 produced which opens on a level with the surface of a water- 

 canal, while the other part is imbedded in the substance 

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

 derneath. Tlius the ampullaceous sac so far resembles the 

 position of a polyp in its fleshy dermal substance ; but here 

 the analogy ceases. 



I have long since stated (1857) that, when treated with a 

 solution of carmine (that is, of carmine water-colour paint) in 

 the living state, the ampullaceous sacs are the only parts in 



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