a- neio Genus and /Species of Spouffes. 193 



the constricted end of the funnel which here joins it, and to 

 be formed, apparently, of much less rigid structure. The sar- 

 codal rug£e are much more openly reticulate, although still 

 tending to a circular arrangement ; and apertures of diiSferent 

 dimensions begin to appear in the interstices of the reticula- 

 tion (fig. 5 ff, A, i). 



One cannot help being struck with the resemblance in form 

 of these rugaj (which are indistinctly fibrous under compres- 

 sion and a high power) to the carnece columnce of the heart in 

 warm-blooded animals ; nor can one help associating the 

 patent character of the canals with this structure surrounding 

 them, and the apertures in the interstices, with the trachese of 

 insects. We see also how the extent of surface thus becomes 

 multiplied, how these projecting rug£e assimilate the structure 

 to that of the frog's lung, where, for aeration, the internal 

 surface of the hitherto simple sac in fishes begins to shadow 

 forth the vesicular character and vast extent of surface ex- 

 posed for aeration in the fully-developed lungs of the mam- 

 malia ; nor can we, finally, fail to conclude that the excretory 

 system of canals in this and probably all other sponges may, 

 at least partly, subserve this purpose. 



I have not been able to pass a bristle from the vent on the 

 surface through the excretory canal in the parenchyma to the 

 cribriform disk of the cup-like body, or vice versa. Neither 

 could it be expected, with so many loose valvular projections 

 intervening, and such tortuous passages, that the top of a 

 bristle would be thus unimpeded in its transit. But a bristle 

 can be easily passed through the truncated ends of the large 

 excretory canals in the parenchyma to the vent on the surface ; 

 and when these canals are compared with the canals into 

 which the funnel-shaped prolongation of the cup-like body 

 empties itself, their structure is foimd to be identical. If this 

 identity alone be not considered sufficient to establish the fact 

 that the cup-like body opens directly into an excretory canal, 

 then the fact that there are no other canals of the kind in the 

 sponge for it to open into but the excretory system is decisive. 

 The bristle for this purpose should be burnt at one end, to 

 give it a round form, or " probe-point." 



We next come to the apertures opening into the excretory 

 canal itself through the interstices of the sarcodal reticulations ; 

 and this brings us to the subject of nutrition, with which the 

 excretory system, in combination with the cup-like bodies, 

 must be as much connected as with aeration (fig. 5 i). 



No doubt many of these apertures are the openings of 

 branches of the excretory canal-system which may belong to 

 as many cup-like bodies ; but then there are others which 



