292 A MONOGRAPH OP THE AUSTRALIAN SPONGES, 



The portion of the sponge exposed to attacks is principally the 

 outer lamella. It is as we shall see below, covered by an immense 

 armour of large sand granules cemented together with Spongiolin. 

 This cortex gives to our sponge a high degree of hardness. 



The surface of the interior lamellae is not covered by such an 

 armour, here we only find small and loose sand granules (Plate 

 XXVIL, fig. 7.) 



A difierentiation in function has taken place between the internal 

 and external portions, they both nevertheless have retained a similar 

 internal structure : both contain the same canal system and ciliated 

 chambers. A difference is only perceptible in the sandy cortex of 

 the two. 



It will doubtlessly strike the reader, that these Auleninae are 

 very similar to certain Asconidse among the Calcareous sponges, 

 which likewise possess an " Inter-canal system " and numerous 

 " Pseudopores" just like our Auleninaj. I refer as an example to 

 the Auloplegma form of Ascaltis cerebrum (1). I established the 

 term Auleninae without one thought of the "artificial genus" 

 Auloplegma and only afterwards it occurred to me that Haeckel 

 had used the same root for his name, which shows better than any 

 description ; as it were in an intuitive manner, how very similar 

 these structures must be. 



It appears to me veiy likely that the Auleninse are not developed 

 from ordinary sponges in the manner indicated above, and that 

 moreover they represent among the Ceraospongise a group similar 

 to the above mentioned Asconidse among the Calcispongiee. 



This is the reason why I place these Auleninte at the beginning 

 of this Order. 



The disadvantages connected with this arrangement are very 

 apparent. The water may })ass through the canal system of the 

 sponge proper more than once, which of course is a bad thing 

 unless there be such arrangements in the distribution of inhalent 

 pores and Oscula throughout the suface of the lamellae to prevent 

 the water which has once been expelled through an Osculum from 

 being inhaled again. 

 (1) E. Haeckel. Das System der Kalkschwiimme. Band III., Tafel S, fig. 6. 



