Relations between Marine Animal and Vegetable Life. 155 



I was, however, at first disappointed in failing to obtain the results 

 anticipated. But this failure, I subsequently found, was due to the 

 general opacity of the wood which was freshly cut, and which? 

 though apparently dry, contained large quantities of sap in the 

 interior. I then carefully dried some of the specimens, when the 

 stresses present became quite apparent by numerous cracks starting 

 in radial directions. The results obtained with these dried specimens 

 were quite satisfactory. 



I now tried to devise some experiments strictly analogous to the 

 optical experiments with chilled glass. For this purpose I cast a 

 cylinder of paraffin wax in a metallic mould surrounded by a freezing 

 mixture. Owing to the great contraction produced by solidification, 

 a hollow depression was formed in the centre, and this produced a 

 distortion of symmetry. It would, therefore, be better to build up a 

 cylinder by successive dippings, the deposited molten layer contract- 

 ing on the solid core. I obtained, however, extremely good results 

 with a cylinder of cast ebonite, in which the stresses present are 

 exactly similar to those in a circular piece of unannealed glass. 



The next series of experiments were undertaken with mineral 

 specimens. I here acknowledge with thanks, the kind help I received 

 from Mr. Hayden, B.A., and Mr. Blyth, of the Geological Depart- 

 ment, in obtaining suitable specimens for my experiments. One 

 very interesting specimen obtained from Egypt was formed by ringed 

 concretion of flint round a central nodule. This specimen exhibited 

 the cross with great distinctness. I also obtained fairly satisfactory 

 results with stalactite. The concretion of calcium carbonate formed 

 inside a pipe by deposits from temporarily hard water flowing through 

 it, would also be found to exhibit this phenomenon. 



" The Relations between Marine Animal and Vegetable Life." 

 By H. M. VERNON, M.A., M.B. Communicated by Professor 

 BURDOX SAKDERSON, F.R.8. Received December 8, 1897, 

 Read January 24, 1898. 



(From the Zoological Station, Naples.) 

 (Abstract.)* 



The object of this research was to determine how the nitrogenous 

 matter excreted by marine animals into the water is removed, and 

 what parts the various forms of vegetable life play in the process. 

 Thus this subject is of interest from its practical bearing on ques- 

 tions relating to the efficient maintenance of marine aquaria, as well 



* The full paper will be published in the ' Mittheilungeu aus der Zoologisclien 

 Station zu Neapel.' 



