1873.] 171 [McCrady. 



presented the appearance of a uniformly homogeneous organic film, 

 in which irregular striae often showed themselves apparently due to 

 the convolutions, and the transparency of the film. The exception to 

 this uniformity, which I observed, was the normal and regular exist- 

 ence of granules or nuclei, usually with a disposition to form clusters, 

 and which on one occasion, at least, I observed to be liberated (ap- 

 parently by the dissolution of the surrounding film), and which then 

 appeared as a swarm of dancing cellules with something like a 

 Brownian movement. Upon the layer of Chlliamoctistes cumulus, 

 the particles of mud brought by the tide are continually depositing 

 themselves, so that it is slowly undergoing burial by this constant 

 accumulation. Never, however, is this burial complete, for it grows 

 upward as fast as it is buried, and if the mud beneath the layer be 

 examined, the presence of Chthamoctistes may be traced downward 

 to a considerable depth, mixed with a constantly increasing propor- 

 tion of mud, so that it is impossible to say exactly where the deposit 

 of mud begins in such a section, or where the traces of Chthamoctis- 

 tes disappear. Indeed, my observations led me to conclude that the 

 whole mass of these mud banks bordering the southern estuaries, 

 would prove to be made up of a sort of organic framework furnished 

 by the endless convolutions and furbelows of Chthamoctistes, with its 

 instertices gradually filled in by constantly deposited mud particles. 

 As the deposit grows, the superincumbent weight increases, the 

 healthy and normal appearance of the Chthamoctistes ceases to be 

 traceable in the lower parts, and the mud appears then more com- 

 pact, but still contains traces of organic life in the form of granules 

 and apparently detached pieces of the endless Chthamoctistes frills. 



The upper healthy portion of the Chthamoctistes growth is ten- 

 anted everywhere by Diatoms and sporules of Algaa in countless 

 numbers, and in less quantity by various forms of Rhizopoda; and all 

 through the mud beneath, the lifeless shells and skeletons of these 

 organic forms are found in abundance. Many examinations of the 

 alimentary canal of the oyster prove that it is the Diatoms and spores 

 of Alga? which constitute its food. The former, especially, are found 

 perfect, or nearly perfect, in the stomach and anterior portion of the 

 intestine, and, as empty skeletons, compose nearly the whole mass of 

 the rejectamenta found in the rectum. A few Ehizopods now and 

 then are found, and also a few antherizoids, which latter do not ap- 

 pear to suffer any diminution of vitality in the stomach and anterior 

 portion of the intestine. 



