142 



REPORTS ON INVESTIGATIONS AND PROJECTS. 



blowing for the previous 10 days without intermission the sea was so rough 

 that it was only possible to work when steaming slowly ahead into the wind. 

 This resulted in a great deal of stray on the sounding wire, so that the num- 

 ber of fathoms of wire run out is greater than the actual depth at which the 

 samples were taken ; these differences will be large for the more superficial 

 samples, but small at greater depths, as the wire strays in a curve whose 

 gradient becomes very steep a little below the surface under these condi- 

 tions. The following temperatures were recorded : 



At this point the station had to be abandoned, owing to the bad weather. 

 The samples down to 160 fathoms were diluted 1 in 100 with sterilized sea- 

 water before plating in peptone agar ; the remaining two were plated undi- 

 luted. At the end of 48 hours the following counts were made, the numbers 

 representing the mean of the number of colonies in the two plates made 

 from each sample. 



The colonies developing in all the cultures were only of two kinds, the 

 denitrifying and the non-denitrifying species, both described in my former 

 report. The non-denitrifying species formed a relatively small proportion 

 of the total, and they were not found at all in any cultures made from sam- 

 ples taken below 250 fathoms. As they appear to be comparatively chem- 

 ically inactive, and as nothing is at present known concerning the part 

 played by them in the metabolism of the sea, they will not be further con- 

 sidered here. 



For the denitrifying species I propose the name of Bacterium calcis, ow- 

 ing to their power of precipitating calcium carbonate from solution in the 

 sea. This property will be considered more fully later in this report. The 

 chief cultural characteristics of B. calcis were described in my former re- 

 port, but it will be as well to repeat them here. 



On potassium malate, or peptone agar media, colonies are visible as minute 

 white specks after 6 to 8 hours when the room temperature averages 29.5 ° 

 C. After about 18 hours the colonies are well developed, they are white in 

 color, circular, but with finely irregular outline, and have a granular appear- 

 ance. Superficial colonies are much elevated at first, but as growth pro- 

 ceeds spread rapidly over the surface of the agar. The deep colonies remain 

 small, circular, and discrete. Growth is somewhat more rapid on the pep- 

 tone agar than on the potassium malate agar, and the older colonies develop 

 a brownish tinge in the center when growing on the former medium. 



