SPONGES 



of sponge individuality which we intend to adopt (see below, p. 89), 

 the first-mentioned series may be termed modifications of the sponge 

 person, and the second, modifications of the sponge colony. Although 

 the two often merge into one another, we may consider them apart, 

 and commence with those cases where the sponge person remains 



Fio. 2. 



Fio. 3. 



FIG. 4. FIG. 5. 



Fio. 2. Young specimens of Clathrina coriacea, Mont., x6. a, Olynthus ; ft, older stage, 

 with three diverticula commencing to form ;. c, still older stage, with diverticula anastomosing 

 to form the tubar system ; d, small colony with two oscula ; osc, osculum ; div, diverticula. 



Fio. 3. Small colony of Leucosolenia Lieberkiihnii, O.S., x 6. osc, osculum ; div, diverticula. 



FIG. 4. Arborescent colony of Leucosolenia complicata, Mont., x6. 



FIG. 5. Creeping colony of Leucosolenia variabilis, H., with numerous erect, and for the 

 most part simple, oscular tubes, arising from a basal creeping stolon, x6. 



single that is to say, where the sponge retains a single osculum and 

 gastral cavity. 



The wall of a primitive vase-like sponge may increase during 

 growth either in superficial extent or in thickness, or in both ways at 

 once. We may consider first the results of an increase in the 



