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LEUCOSOLENIA. 



A simple Sponge of the Ascon type, and an example of 

 the Class Calcarea. 



What is the General Appearance of Leucosolenia, and where 

 is it found ? 



It is a small white tubular sponge. The wall of the 

 tube is perforated by numberless minute inhalent pores, 

 and at the top of the tube there is a large exhalent aper- 

 ture (the osculum). The cavity is cut across a little way 

 below the osculum by a thin porous membrane. 



These tubes are massed together in colonies; they 

 arise in numbers from a creeping stolon which grows and 

 branches, forming a horizontal network basis attached to 

 seaweeds, stones, and rock-surfaces. The upright tubes 

 by vegetative budding also branch to some extent. 



Mesogtea - ._ J fc Ijh-Dermal Layer 



Choanocytes of 

 Gastral Layer 



lent Canal 



FIG. 14. Transverse Section of an Ascon Sponge (Leucosolenia). 

 ( Diagrammatic. ) 



Describe the Structure of an Ascon Sponge (Leucosolenia) 

 as seen in a Transverse Section of the Body. 



The wall consists of an outer dermal layer and an inner 

 gastral layer with a middle jelly between these layers. 

 The breaks in the wall are the short inhalent canals 



