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 



Fig. 2. 



Fio. 3. 



Fig. 4. 



Fig. 



Fio. 2. — YounK sppriniPiis of Clnthrino, corimra., Mont., xO. a, Olynthu.s ; h, older stage, 

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

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



Fio. 3. — Small colony of Lciicosolenia Lieberkiihnii, O.8., X6. osc, osculum ; div, diverticula. 



Fio. 4. — Arborescent colony of Leiicosolenia complicata, Mont., x6. 



Fio. 5. — Creeping colony of Leucosolcnia variahilis, H., with numerous erect, and for the 

 most i)art simple, oscular tubes, arising from a ba.sal creeping stolon, x 6. 



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 



