58 



DEPARTMENT OF THE NAVAL SERVICE 



TABLE XI. 

 Bathymetric Range. Station 6. August 15. 



I regret that time did not permit a more thorough examination of the conditions 

 at Station 3. From the results obtained it appears that the most favourable level is 

 from 10-20 metres, and that below that depth a rapid decrease may be expected. One 

 form, Melosira sulcata, which is not uncommon in surface waters, ,has been found on 

 one occasion to be greatly increased at lower depths. Diatoms are by no means rare 

 at a depth of 175 metres. 



Cultures. 



To ascertain whether other diatoms were present at any level in such small 

 nvimbers that their presence was undetected by centrifuging, or were perhaps present 

 in the form of spores, too minute for observation (3), cultures were started from water 

 obtained at each level from Station 6. To this end a beaker of one litre volume was 

 half filled with water drawn from each level. The water was treated by Miquel's 

 method (18) as improved by Allen (9). This treatment is dealt with in a later paper 

 on Culture Methods. The six cultures were then placed in the most favourable situa- 

 tion for growth. No strictly plankton forms others than those listed in the tables, 

 developed; but Schizonema Grevillei, roped in long beautiful strands, appeared in 

 abundance in every beaker; and Melosira Borreri produced several normal chains in 

 the water from 7 metres. It may then be concluded that other forms were lacking 

 for, although the specific differences are such that diverse conditions are necessary for 

 obtaining permanent cultures of the many forms, I have found that the method here 

 employed has given a greater or less initial growth for all the plankton diatoms so 

 treated. 



