271 



culuiu of Geodia barretti. ') The size of the sponge is from 5 to 

 25 c. m. iii largest diameter. The colour is pale butf, dirty white, 

 greyish or pearl-coloured. 



A section through the living animal shows a bluish or yel- 

 lowish pareuehyme and an almost white cortex. Accordiug to 

 the shape of the sponge the outliue of such a sectiou will be 

 regular or uot. The cortex, which is rather thin, is perforated 

 by straight little canals, already visible to the naked eye. These 

 cauals are the excurreut aud incurreut chones, which end in the 

 parenchyme in rather straight cauals. 



On the surface of the sponge a quautity of spots are visible, 

 which , to the naked eye seem to be pores. These spots are however 

 no pores at all, but correspond to the lumina of the chones. A 

 thin tangeutial section shows under the microscope that on the 

 spots, mentioned above, there are groups of stomions, of which 

 about ten lie together. Sections at right angles to the surface of 

 the sponge and passing through a chone, help us to understand 

 how the entrances of the canal-systera are. There is a distinct 

 diÖerence between endochone and ectochone. The latter begins 

 with a wide funnel, the equivalent of the subdermal cavities in 

 other sponges. On this funnel follows a long, straight, narrow 

 tube (ectochone) , which communicates in the ordinary way with 

 the short dome-like endochone. Immediately. in communication 

 with these endochones are the subcortical crypts. The system of 

 ramifying incurreut cauals, either starts from here or we have 

 first a few canals which start from the crypts, and after a while 

 uüite again in lacunae. Such seems to be the case in large spe- 

 cimens . and we see then that the ramifying cauals begin only 

 after these lacunae i. e. nearer the sponge-centrum. The incur- 

 reut canals eud iuto rather short and not very narrow prosodi. 

 The flagellated chambers are hemispherical , resembliug those of 

 Euspongia e. g. ; they are not very numerous. The aphodi are 



1) There are however distinct anatomical differenccs between the cloacas of Geodia 

 barretti and tlic Cvdonium here mcnlioncd. 



