258 BACTERIA IN THE SEA [PART III 



at great distances from the land. Bacilli occurred but they were 

 not numerous. The predominant bacterial species in the open sea 

 are spirallar or bent rods, chains of commas, or twisted corkscrew- 

 like forms. Fischer shews that there is great diversity in the 

 moi^hological characters of oceanic bacteria, but that, as a class, 

 they are distinguished by the following features: (1) they are 

 either bent rods or spirals ; (2) they exhibit a decided preference 

 for food solutions containing salt in the proportion in which this 

 occurs in sea water; and (3) they are often self-luminous. It is 

 true that many land forms exhibit these characters : thus the 

 cholera germ, and the associated group of vibrios, have the form 

 which is characteristic of the oceanic species ; some land forms can 

 live in highly saline solutions; and Kutscher has shewn that a 

 l^acillus may be present in the human intestine that may be self- 

 luminous \ But as a group these characters distinguish the truly 

 oceanic from the land bacteria. 



Halibacteria. This is the general term (quite a loose one of 

 course) which has been applied to the marine bacteria. They can 

 live and multiply in sea water containing no added food salts, or 

 other substances. This was repeatedly proved on the Plankton 

 Expedition when water taken from the sea was at once placed in 

 sterilised test tubes, and in a few days it was found that decided 

 multiplication had taken place. They are almost exclusively 

 aerobic bacteria, living in the presence of oxygen, but many can 

 function as facultative anaerobes, that is they can live in solutions 

 containing no free oxygen. Their reaction to temperature varies 

 greatly, thus Halihacterium peUucidam has a wide range of 

 temperature, some luminous bacteria grew and produced light at 

 the freezing point of fresh water, others multiplied at 3° to 5° C, 

 others again at 10°, and one even at 46° C. In no case did Fischer 

 observe endogenous spore formation, that is the formation of a 

 spore within the vegetative growing cell; nevertheless he was able 

 to keep some of his cultures on agar for 2^ years. All halibacteria 

 are more or less motile. Some appear to be pathogenic: when 

 introduced into the peritoneal cavity of guinea-pigs or mice, death 

 of the host took place and the bacterium could be obtained from 



1 Deutsche medicinische Wochenschrift, No. 49, 1893. 



