No. 3.] DEVELOPMENT OF MARINE 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 abundant 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 Pl. XV, Fig. 12, are shown a young 
larva, 7, a full sized gemmule, g, medium sized gemmule, 2’, 
and several little gemmules, ¢”. In the section Pl. 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 
