390 SCIENCE PROGRESS. 



bacteria in the ocean where they play (as on land) the part 

 of middleman between death and life, by causing the pu- 

 trefaction of dead bodies of animals and plants — in other 

 words by transforming dead organic substance into simple 

 inorganic combinations to be used by plants and thus 

 restored to the circulation of organic matter. This cir- 

 culation of organic matter, as we know it on land, has 

 hitherto been only guessed at in the deep, and Dr. Fisher 

 and Messrs. Mcintosh and G. Murray have, as it were, 

 completed the two gaps in our knowledge of the circle. 



Very little was known of the existence of bacteria in the 

 sea when the Plankton Expedition sailed. Dr. Fischer had 

 made his earlier observations, and after the return of the 

 expedition, and before the publication of his memoir, Dr. 

 Russell ^ made investigations in the Bay of Naples ; these 

 with the work of De Giaxa^ practically exhaust the litera- 

 ture of marine bacteria. That the bacterial contents of the 

 sea are being constantly influenced by the land is a fact 

 beyond doubt. The sea is not only constantly receiving 

 bacteria from the land, but all manner of such substances as 

 nourish bacteria. A very poor estimate can be formed of 

 the numbers carried by the winds to the sea, but we know 

 that the rivers which are, many of them, little better than 

 drains of organic matter are every moment conveying 

 myriads to the sea. Nothing is more astonishing, how- 

 ever, than the rapid manner in which the sea, as it were, 

 disposes of them. De Giaxa and Russell made experiments 

 at varying distances from the opening of the sewer canal at 

 Naples, and they found that at three kilometres from the 

 shore the influence of the land w^as no longer recognisable. 

 Similar observations made at Kiel, where the haven is more 

 land-locked, gave a slightly different result, but it may be 

 taken as generally true that the coastal waters, often very 

 rich in bacteria near the shore, are generally quite free from 

 the influence of the land in this respect at from three to five 

 kilometres out to sea. Even, however, at places farthest 

 removed from land, bacteria are present as a rule and at 



^ Zeitschrift fiir Hygiene u?id Infectionskrankheiten, Bd. vi. - Il>id. 



