BY R. VON LENDENFELD, PH.D. 489 



The depressed portions of the surface between this network are 

 the pore sieves. Thin unprotected membranes perforated by the 

 inhalent pores. These pores are very remarkable and different 

 from the inhalent pores, usually observed in horny sponges, in as 

 much as they are very large and few in number. One or two in 

 each field only. They measure 0'03 mm., on an average in 

 diameter and are circular. 



The canals leading down from them into the body of the sponge 

 shall be described further on. 



This net structure of the surface is developed in a similar manner 

 in the j&elds between the conuli and on the aconulous portions, as 

 also in the surface of the vestibule spaces. 



It is absent only in the surface of the true canals of the sponges 

 and consequently a very useful structure in determining which 

 canals are true canals and which are vestibule spaces. 



CANAL SYSTEM. 



A, Vestibule Spaces. 



As mentioned above, some of the varieties of this species possess 

 very highly developed vestibule cavities, which however are, as 

 pointed out above, by no means homologous to those described in my 

 last paper on Auleninae. As no oscula are met with in their surface 

 they might be considered as portion of the inhalent system. But 

 the transision forms which connect these vestibule varieties with 

 irregular digitate forms without vestibules are of such a natiire as 

 to preclude their acceptance in this sense. RefeiTing to the 

 formation of these Auloplegma structures described in my paper 

 mentioned above I would like to draw the attention of the thinking 

 reader to the different result attained in the two sub-families 

 Sponginee and Auleniaee by the further developement of this 

 interesting structure. 



