172 ARTHUR DENDY. 



entire genus (Hypograntia) on the supposed presence of such 

 "large holes of inter-communication between the chambers." 



On the whole it appears to me that Sycantha ten el la 

 probably presents a slight modification of the simpler Sycon 

 type of canal system^ having the radial chambers united in 

 groups. 



Grantia (figs. 9, 10). 



The canal system of this genus may be regarded as derived 

 from the Sycon type by the conversion of the thin^ pore- 

 bearing, dermal membrane which we first met with in Sycon 

 gelatinosum (figs. 3 and 6) and then, with the addition of a 

 few spicules, in S. boomerang (figs. 7 and 8), into a more or 

 less strongly developed spicule-bearing cortex, which not only 

 extends between the ends of the radial chambers, but also 

 covers them over, so that we no longer find in this genus 

 distal cones projecting from the dermal surface. 



A thoroughly typical example of the genus is afforded by 

 the Australian Grantia extusarticulata (4), the anatomy 

 of which is represented in fig. 9. The radial chambers are 

 almost straight, cylindrical, and only slightly branched; 

 between them lies the irregular and more or less lacunar 

 inhalant canal system. The dermal or inhalant pores are 

 irregularly scattered through the dermal cortex, which is well 

 developed and about 0-07 mm. thick. The gastral cortex is of 

 about the same thickness, and is perforated by the short, wide 

 exhalant canals; one coming from each chamber, and separated 

 from it by a constricting diaphragm. 



Grantia Vosmaeri (4), another Australian species, whose 

 anatomy is represented in fig. 10, illustrates in an extremely 

 interesting manner the gradual shortening of the radial 

 chambers and the corresponding elongation of the exhalant 

 canals, accompanied by a strong development of the mesoderm 

 which surrounds the latter. Here, again, the junction between 

 exhalant canals and flagellated chambers is clearly marked by 

 well-developed diaphragms. The dermal cortex is very thick, 

 and the dermal pores communicate with the deeper parts of 



