On a Pamsitio Sponge. By Prof. P. Martin Duncan. 381 



and the other was broken into two parts. One of them was placed 

 on a slide under a low power, and dilute nitric acid was added to 

 the small quantity of water in which it floated. The whole dis- 

 appeared during a rapid effervescence. The second part was 

 placed in much water, and was well washed, and it became much 

 more tiansparent. It polarized like the specimen already alluded 

 to ; and as minute quantities of the acid solution wore added, it 

 gradually disappeared, leaving an excessively delicate organic film 

 behind. 



The portion which had been mounted in Canada balsam became 

 transparent, and on the application of the polarizing apparatus it 

 not only gave indications of the presence of carbonate of lime in 

 minute particles, but of two needle-shaped spiculfe which traverse 

 it and which are calcareous. The tissues are exceedingly thin, 

 however, and their microscopic details are not so perfectly visible 

 as those of the larger specimen first mentioned. The spicules 

 within this specimen are very small aciculate, but with rather an 

 angular transverse outline. 



Many calcareous spiculae are to be noticed free in the Canada 

 balsam in the specimen first described, and in one of the chambers 

 of the Carpenteria there is a sac which has been cut across, and it 

 overlies a triradiate and polarizing spicule. It does not appear, 

 however, to have any organic connection with it. 



The spiuules on the cellular membrane of the specimens are 

 calcareous, and in their shape they resemble the larger and corre- 

 spondingly placed spicules of some Calcarea. 



The membrane is stiff, and has the power of not collapsing 

 under some pressure, and the tube-hke stolons keep their form 

 after fracture. 



It has been noticed that the sections of Carpenteiia which are 

 mounted in Canada balsam contain two other specimens of this 

 remarkable organism — one being fragmentary and consisting of 

 two small sacs united by a stolon, and the other being a parent 

 sac which has been cut in half. This last approximates probably 

 to the shape of the interior of a small foraminiferal chamber, and 

 traces of stolon growth are only visible at one of the terminations of 

 the body. The question arises very naturally. Do these bodies 

 ever fill up the foraminiferal chambers and line them ? I\[any of 

 the cliambers of the Carpenieria are lined with a membranous- 

 looking tissue, but it cannot be identified. 



There is a specimen of the ordinary Carpenieria which has 

 covered in part a Porites, and Dr. Carpenter many years since 

 made sections of it to indicate the presence of sponge spicules 

 within its chambers. These are siliceous spicules, and evidently 

 jiertain to a Cliona. But a careful examination of one of the 

 chambers proves that several were once occupied by a body greatly 



