ZOOLOGY AND BOTANY, inCKOSCOPY, ETC. 785 



triple cell were the product of an amputated quadi'uple cell which 

 had originated from double division of a double cell, there must 

 necessarily be found either at the beginning or the end an enclosed 

 shell, since the quadruple formed regularly from the double cell can 

 only have the formula fee ff e e f. 



The formula f e f e e f, which can be positively demonstrated in 

 all triple cells, can only be explained on the assumption of the 

 hypothesis of there being two shells ; it is quite incomprehensible on 

 the assumption of a simple hoop, unless the most complicated process 

 is arbitrarily supposed. 



Whilst triple cells frequently occur in T. americana, only once 

 was a quadruple found the origin of which was clear. The 

 examination of this gave the formula f e e f e f e f . This formula 

 shows first of all that this quadruple could not have originated from 

 the regular division of a double, but must necessarily have been 

 derived from a triple cell ; further, it completes the proof of the 

 Macdonald-Pfitzer hypothesis, since every other explanation of its 

 origin appears inadmissible. 



Remarkable Vital Phenomenon in the Adriatic* — In the year 

 1872, and again in 1880, a remarkable development took place on 

 the surface of the Adriatic, in the neighbourhood of Trieste, of a 

 mucilaginous floating substance, in such vast quantities as to seriously 

 interfere with the fishing. This has been examined by Count (Abbe) 

 Castracane, who attributes it to the extraordinary multiplication of 

 various diatoms, in opposition to the view of Zanardini, by whom it is 

 attributed to a new alga called by him Dermoglcea lirni. The diatom 

 which plays the greatest part in the formation of the slime ajijiears to 

 be Nitzschia macilenta, accompanied, however, by numerous other 

 forms ; and the mucilage, shown by chemical tests to consist of 

 cellulose, is its ordinary gelatinous envelope. The researches of the 

 • Challenger ' have shown that diatoms are not imiformly distributed 

 through the deep sea, but are found especially near the shore, and in 

 colder and brackish water. The time of the year when the pheno- 

 menon in question was observed, Juue and July, favours the hypo- 

 thesis that it was partly due to the rapid melting of the snow on the 

 Alps and the Apennines, which brings down an immense quantity of 

 fresh and cold water into the Adriatic : and that the extraordinarily 

 rapid multiplication of the diatoms was promoted by the great 

 stillness of the water. The phenomenon was accompanied by a 

 remarkably brilliant phosphorescence caused by myriads of Peri' 

 dinium (Ceratiiim) belonging to several species. 



Uses of Diatoms. t — As a supplement to Dr. M. Lanzi's paper, 

 referred to at p. 512, may be mentioned an article by 3Ir. H. G. 

 Hanks, State Mineralogist of California, in which he enumerates the 

 following additional uses of diatomaceous earth : — 



" It is a very convenient soui'ce of soluble silica, employed in the 



* F. Castracane, ' Straoidinario Fenomeno della vita del mare, osservato nell' 

 Adriatico nella estate del 1880.' Eoma, 1881, 13 pp. Estiat. d. Atti Accad. 

 Pontif. Nuovi Liucei, xxxiv. 



t 'Mining and Scientific Press,' July 9tli, 1881. 



