NOTE ON WALTKKIA LEUCKAUTI 13 



ight from the desiccated, pure white tissues might cause an illusion 

 as to the real condition of the cavity in the deeper part. So a probe, 

 made of a soft paper rolled up into a flexible thread, was made use of to 

 ascertain the matter. From the side of the orifice, it could not be 

 introduced for more than 4 or 5 mm., ami by inserting it in the contrary 

 direction from the stem lumen, it could never be managed so as to bring 

 its end into view through the terminal orifice. It was evident that the 

 terminal cavity really had a bottom, — that it was partitioned off from 

 the lumen of the stem by a tissue exactly like that of the wall. Finally 

 the sponge was carefully cut open at the part ; but this did not help 

 much in making the matter any clearer, owing to the disturbance that 

 was inevitably caused to the brittle tissue by the scissors. 



In the specimen in question, at any rate, I believe the partition was 

 -there. But the partition should probably be considered as only an 

 apparent, not a real, one. For, it seems perfectly justifiable to assume 

 that the spaces on both sides of it represent parts of one and the same 

 ■excurrent space of the sponge, or in other words, that, in the natural 

 state before desiccation, they stood in open connection with each other 

 by one or more narrow excurrent canals running through it. This 

 partition may then be considered simply as a thickening of the wall 

 inwards so as to narrow th ' continuous internal passage at the part. 

 The relation between the terminal cavity and the stem-lumen should 

 have been just the same as that which ohtains in certain pedunculated 

 Hexactinellids (f. i., Saccocalyx pedunculata F. E. Sch., among the Eu- 

 plectellidie) betweeen the gastral cavity contained in the body proper and 

 the hollow of the stalk, which latter is only an extension of the excurrent 

 canal system. It of course remains to be seen whether this is to be 

 looked upon as an indication that Walter ia leuckarti is a stalked form, 

 in which the hollow stalk is so extraordinarily developed as to represent 

 the essential part of the entire sponge and in which the body proper 

 forms so quite an insignificant portion at the apical end ns to be said as 

 being in the verge of disappearance. Above all things it remains yet to 

 be established by futur; observations that the occurrence of the partition 



