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generally a little wider tban the prosodi ; sometimes they are 

 extremely short. After having been united with neighbouring 

 ones, the excurrent canals end iuto crypts , from which the water 

 passes into endo- and ectochones. These resemble the iucurreut 

 choues , ouly being a good deal wider. The ectochone is covered 

 by the dermis in which a group of proctions are visible. The 

 excurrent chones lie together in one , seldom more shallow depres- 

 sions of the sponge-surface. There are frequently 100 — 200 excur- 

 rent chones in one depression, 



The cortical skeleton cousists chiefly of sterrasters ; the dermal 

 skeleton of one or more layers of chiasters. In addition to these 

 some of the long parenchymal anatriaeues protrude till beyond 

 the surface of the sponge; but these are not abundant. On the 

 ether hand there is a number of microxeas and delicate anatriaenes , 

 projecting with the cladome. As they are never fouud very deep 

 in the cortex they may be considered as dermalia ^). They do 

 not occur however in the dermis which covers the chones. 



The chief part of the parenchymal skeleton consists of long 

 oxeas. They radiate in more or less distinct bundies from the 

 centrum of the sponge. Towards the cortex anatriaenes make there 

 appearance. Close under the cortex the oxeas become rare and 

 here anatriaenes, orthotriaenes and protriaenes prevail. The cla- 

 domes of the orthotriaenes form a distinct layer just beneath the 

 cortex and above the crypts. Only a few orthotriaenes lie deeper 

 in the parenchyme. 



In the peripheral parts of the sponge the arrangement of the 

 parenchymalia is merely a radial one. In the parts which are 

 near to the centre , there are always some oxeas in a concentric 

 position , i. e. at right angles to the radial bundies. I found this 

 in many sponges, where the skeleton is for the rest a radiate 

 one; a fact which seems to have escaped the attention of other 

 observers. 



1) These dermal anatriaenes are only seen in very carefully prepared specimens as the 

 fine cladome easily breaks off. 



