66 



DEPARTMENT OF THE MVAL SERVICE 



From the above it may be judged that the most favourable development may be 

 expected in strong, diffuse light and with access to the air. It may be added, however, 

 that the difference between the flasks in position 3 was one of quantity and not of 

 quality. Both contained long, beautifully formed chains, without any signs of dis- 

 integration; and a later trial showed that if the plug were removed every few days 

 to permit a change of air, the growth could be maintained. To prevent the entrance 

 of foreign substances and undue evaporation the latter plan was then adopted'. 



In several of these cultures the terminal frustules frequently enlarged to form 

 large g'obular cells. The outer valve was cast off and the contents of the whole frus- 

 tules issued, but remained closely bound to the inner valve, and encased in a firm, 

 transparent wall. These cells were filled with dark, dense contents. Later they divided 

 to form long, regular, broad chains. These sporangial frustules and consequent broad 

 chains were most abundant in the flasks placed in the south window, and particularly 

 S) in that which wrs closed; a few appeared in the north window, and an even smaller 

 number were noted in position 3. A further consideration of these will be given in a 

 later section. 



The cultures placed in the dark showed a very considerable -development. Growth 

 was not profuse but after two months many chains were still in good condit'on. At 

 that date it was noted that no sporang^al cells had developed, that the chroma- 

 tophores wer? decidedly greener than those in the light and that the divisions were 

 often irregnlat and the frustules distorted. The material was then divided and part 

 removed to favourable light conditions. There it revived to a considerable extent, 

 but the chains displayed much more malformation then in normal cultures. The 

 port'on left in the dark continued to live and on January 12 a few enlarged end cells 

 were noted. On March 15, six months after the culture was set up, living cells were 

 still to be found, although they were not abundant. Most of the chains were empty 

 and it is worthy of note that fully half of them had developed from the sporangia 

 noted on January 12, for they were on an average 36 jx in width. 



A culture in which broad chains were particularly numerous produced, when 

 removed from the south window, a fairly healthy, normal colony, in which no broad 

 chain=* were found after two months development. It may then be inferred that in 

 an actively growirg culture the older cells are dissolved and thus retard the exhaustion 

 of food material by the growing cells. In the colony exhausted by life in the dark 

 d'ssolution did not take place and the empty cases remained. 



II. Salinity. — To test the development with respect to the concentration of salts 

 a series of cultures was set up in treated sea water, sttengthened by evaporation, or 

 diluted by the addition of tap water. The latter was used owing to the lack of dis- 

 tilled water and I am indebted to Prof. Alex. Vachon for the following analysis of 

 its contents. The sample analysed contained 0.0225 g. of residue per _ thousand, 

 which was composed of a trace of chlorides, a little calcium carbonate and fine sand. 

 The series was set up on November 25 and gave the following results: — 



Concentration. 



Tap water 



Tap + Mlquel sol . 



10% Sea 



25% " 



40% " 



50% " 



60% " 



75% " 



90% " 



100% " 



125% " 



150% " 



175% " 



200% " 



December 9. 



Fair. 



Dead. 

 Good. 



Excellent. 



January 27. 



Deteriorated. 



Deteriorated. 



Improved- 



Excellent. 



Fair. 



Poor. 

 Little life. 



