STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 179 



and arranged radially around the exhalant canals, features 

 which characterise von Lendenfeld's family Sylleibidse (10). 



The only instance of this Syllectoid condition which I have 

 myself observed in the genus Leucandra is in the case of L. 

 australiensis (4), the anatomy of which is represented in 

 fig. 17. This is a rather large, solitary species^ of the typical 

 sac-shaped form. The flagellated chambers are irregularly 

 sac-shaped, and average about 0"3 by 0*1 mm. in size, though 

 very variable. Their radial arrangement around the exhalant 

 canals is not nearly so well marked as in some other species to 

 be mentioned directly ; but it is obvious that the chambers of 

 any sponge must be arranged more or less radially around these 

 canals if, as in Leucandra, a large number open directly 

 into them. 



In Leucandra aspera, according to Vosmaer (14), we find 

 much the same condition, except that the radial arrangement 

 of the somewhat elongated, sac-shaped chambers around the 

 exhalant canals is more regular, a condition which is very 

 closely paralleled by Leucilla uter (vide infra and fig. 21). 



Von Lendenfeld's Polejna telum and Vosmaeria corti- 

 cata (10), both of which belong to the genus Leucandra as 

 here understood, likewise afford, according to this author's 

 figures, good illustrations of the more regular Sylleibid type 

 of canal system, with the flagellated chambers somewhat elon- 

 gated, and arranged radially around the exhalant canals. 



This Sylleibid condition, first described by Polejaeff (8), 

 appears to be intermediate between the typical Syconoid and 

 the typical Leuconoid conditions, but approaches more nearly 

 to the latter than to the former. Indeed, it would be extremely 

 difficult to say where the Sylleibid condition ends and the 

 Leuconoid begins, for even in such a typically Leuconoid form 

 as L. phillipensis (fig. 16) some of the chambers, especially 

 towards the outside of the sponge, may be markedly elongated, 

 and thus approach the Syconoid type ; and the same variation 

 in the form of the chambers is found to an even greater extent 

 in some species belonging to other genera, as will be seen later 

 on. This fact, and the fact that the Sylleibid type of canal 



