488 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



Surface. 



The surface of Euspongia irregularis specimens of all varieties 

 is the same. It is covered by small conuli, close to one another 

 throughout. vSuch conuli are also observed in the surface of the 

 vestibule cavities. They are not very regularly disposed, so that 

 the fields between them become slightly ii-regular. They are on 

 an average 2 mm. apart and 1 mm. high rounded at the top. 

 Often two adjacent conuli coalesce whereby the irregularity in the 

 configuration of the surface is much increased. Sometimes there 

 are zones 3 mm. in breadth without conuli {Euspongia irregularis 

 JacJcsonia,) running up one side of the digitate processes in a 

 longitudinal direction. These ai'e homologous to the ones more 

 minutely described further on of the species Eus2}ongia ca^iali- 

 culata ; they are, however, not met with in the other varieties in 

 so distinct a developement, although also in these indications of 

 aconulose patches are observed. 



The oscula are scattered over the outer surface of the sponge in 

 an irregular manner. In those specimens which possess aconulous 

 zones we always find the oscula in these zones. The oscula are 

 are circular and measure from 1-4 mm, in diameter. 



Slightly magnified the surface presents the appearance of a very 

 regular network. The meshes of this network measure from 0-1-0 "4 

 mm., in diameter and are always of uniform size throughout the 

 surface. 



In Euspongia irregularis siUcata they are the largest — 0*4 mm., 

 and in the variety Jacksonia the smallest, measui'ing 0*1 mm., across. 

 This network is formed by a system of raised lines on the surface, 

 which are about as broad as the depressed meshes between them. 

 In these raised lines an abundance of sand grains and other 

 foreign bodies is generally met with. These give to the whole 

 the appearance of a sand net. This sand net is very regular. 

 Long siliceous spicules are found in it in great masses. These of 

 course are foreign and only collected and not produced by the 

 sponge. 



