592 BEPOKT— 1882. 



4. The injvnous Parasites of JEgypt in relation to Water-Brinlcing, 

 Btj Dr. COBBOLD, F.B..S. 



The author stated tliat tlie most daugerous parasites were Bilharzia hfematohia 

 and Anchylostoma duodenale. To avoid infection by the larvte the following rules 

 were recommended : — 



1. To select for drinking purposes, whenever procur.ible, either deep well water, 

 or water from a spring collected at or near its source. 



2. To avoid the use of stagnant water of any kind, especially that procured from 

 tanks or shallow pools. 



3. If the only water available for drinking purposes has been obtained from a 

 doubtful source, it must either be thoroughly filtered or boiled : merely straining 

 through muslin or other of the coarser kinds of filter is useless. On excursions or 

 shooting expeditions a pocket filter must be carried. 



4. Avoid partaking of all salads made with vegetables grown either in market 

 gardens or in open situations frequented by natives of uncleanlj- habits. Lettuces, 

 water-cresses, and other uncooked vegetables, even when they are known to have 

 been cultivated in favourable situations, require to be carefully washed with clean 

 water befoie use. Only spring water, well water, filtered water, boiled water, and 

 distilled water can be pronounced as absolutely safe : springs near human habita- 

 tions are liable to become contaminated.' 



5. On a neio Principle affedlvg the sijstematic Bistribution of the Tor- 

 pedinidoD, and on the prohahle occurrence of the T. occidentalis (Storer) 

 on the British Coast. By E. DU Bois-Reymond, F.B.S., Professor of 

 Physiology in the University of Berlin. 



Professor Gustavus Fritsch, who is at the head of the biological department of 

 my physiological laboratory, is engaged in a series of researches on electric fishes, 

 which he has pursued, since last autumn, in Egypt, Asia Minor, and on the shores 

 of the Mediterranean, at the cost of the Humboldt Foun<lafion for Natural Science 

 and Travels, dependent on the Berlin Academj- of Sciences. Among Professor 

 Fritseh's results there is one which, highly remarkable in itself, seems to me 

 particularly calculated to interest British zoologists, and I therefore venture to ay 

 before the Section a brief abstract of this pai-t of his work. 



The researches of Professor Babuchin of Moscow, on the development of the 

 electric organs of the torpedo, have established beyond a doubt that these organs 

 are formed by the metamorphosis of striated muscle, and that, once formed, they 

 increase in size only by the growth of the columns or prisms of which they consist, 

 and of the transverse septa of tliese columns, never by the formation of new 

 columns and septa, or of new electric elements. Setting aside individual variation 

 the number of columns, therefore, is the same in j'oung and in adult specimens. 



The latter fact had already been stated, many years ago, by delle Chiaie of 

 Naples, and he had arrived at the same conclusion as Professor Babuchin. Later 

 on, the preformation of electric elements was impugned by Professor Valentin ; 

 but Rudolpli A\^agner, with the assistance of Professor Ijeuckart, then one of his 

 pupils, proved delle Chiaie's statement to be correct, for he found about the same 

 number of columns in the foetus of torpedo and in the adult fish. As the law of 

 the preformation of electric elements was first established by means of a census of 

 the columns in young and adult specimens by delle Chiaie, and afterwards deduced 

 from embryological facts, and, as it will be seen, generalised by Professor Babuchin, 

 it appears proper to stjde it delle Chiaie's and Babuchin 's law. 



Professor Babuchin, by embryological investigation, has shown the same law to 

 apply to the imperfect electric organs of the common ray, oidy that these organs 

 are formed of striated muscle which in its development has reached maturity, 

 whilst the organs of torpedo are formed of muscle in an embryonic state. 



' Full reports of this paper are given in Nature, September 14, and in the British 

 Medical Journal, September 16, 1882. 



