No. 3-] DEVELOPMENT OF MAREVE SPONGES. 287 



Kleinenberg's picric proved itself of use for special points, 

 often preserving the individual cells in a more natural and 

 uncontracted condition than the Zacharias. But in general it 

 dissociated the elements too much. Borax carmine and hae- 

 matoxylin stained in a very satisfactory way. For macerating 

 purposes Bela Haller's mixture was chiefly used. 



2. Formation of Gemmules. 



Any portion of the sponge body may develop gemmules. 

 They may be found in the extreme peripheral region, visible 

 under the surface of the uninjured sponge, or may be present 

 in the center of the body. In whatever region they are found 

 they are usually so abundant as to greatly change the structure 

 of the sponge body in that district. In many Esperellas, dur- 

 ing the summer, the whole body seems given over to the 

 formation of gemmules. In such individuals gemmules are 

 thickly scattered through every part, and the organization of 

 the entire sponge is seriously interfered with. (This inter- 

 ference, as will be shown later, consists largely in the reduction 

 in number of the flagellated chambers, in the obliteration of 

 many canals, and the rupturing of trabeculae.) In other indi- 

 viduals the gemmules may be extremely abimdant in certain 

 portions of the body, while the normal sponge structure is 

 retained elsewhere. The older gemmules and the larvae are 

 easily seen with the naked eye. All gradations of size are 

 found down to minute gemmules consisting of but a few cells. 

 The older gemmules and larvae project into the larger canals, 

 the younger gemmules lie in the trabeculae imbedded in the 

 mesoderm. In the section PI. XV, Fig. 12, are shown a young 

 larva, /, a full sized gcmmule, g, medium sized gemmule, ^ , 

 and several little gemmules, _^". In the section PI. XIV, Fig. 8, 

 four young gemmules of different sizes are shown lying in the 

 mesoderm. 



The formation of gemmules in large numbers is associated 

 with a certain degeneration of the normal sponge structure. 

 This is evident when sections through a region in which gem- 

 mules are numerous (PL XIV, Fig. 8) are compared with sections 



