1903.] with especial Reference to its Nitrogenous Metabolism. 4G5 



allowed to go free in the liquid. - With the object of settling this 

 point, cultures which had manufactured a good deal of albuminoid 

 ammonia, were subjected to centrifugalisation, and analyses made of 

 the clear solution (see Tables VI b (analysis No. 3) and Y). The clear 

 solution in either case contained no more albuminoid ammonia than 

 the control, proving that the elaborated nitrogenous substances were 

 entirely retained within the cell body. 



In two cases, however (Tables YI b (analysis No. 4) and YII b), 

 older cultures were examined. The word " older " is here used to imply 

 that these cultures had passed through many more cell-generations, 

 judging from the appearance of the growth and the size of deposit 

 present. In these cases, a considerable amount of albuminoid ammonia 

 was found to exist in the clear liquids. This seemed to prove that 

 the algal individuals, under certain conditions, yield up to their 

 culture liquid somewhat complicated nitrogenous matters in a soluble 

 form, and a probable explanation Avould be that they exhibit this 

 phenomenon when the cells are in a dying or dead condition. This 

 fact assumes a certain significance when it is remembered that the 

 natural habitat of this alga is ammoniaeal liquids, hence notably 

 polluted waters. The actual amount of assimilation and excretion 

 is extremely small, and it would be difficult to assert that the 

 presence and growth of such an alga as Chlorella pyrenoidosa was 

 of very great importance in nature. But the effect of this alga, if 

 present, would probably be to leave the water, in which it has gffown, 

 in what would be termed a " more impure " condition. It is evident 

 from the above experiments that the organism possesses the faculty of 

 converting saline ammonia into albuminoid ammonia, which, under 

 certain conditions, is discharged from the cells into the culture fluid. 

 " Albuminoid ammonia " is a name given to a certain class of sub- 

 stances on account of facts connected with their analysis ; these 

 substances are quite unstudied, and, in this instance, may be perfectly 

 harmless compounds. But the presence of albuminoid ammonia to 

 more than a very small degree has always been considered, perhaps 

 without sufficient foundation, to show evidence of dangerous pollu- 

 tion, and hence to be most prejudicial to any water. The formation 

 and excretion of such compounds by a green alga appears to be a 

 new phenomenon, and is not without especial interest in this 

 connection. 



An attempt was made to compare the nutritive value for Chlorella 

 pyrenoidosa of various nitrogenous substances, and with this object a 

 series of nutrient fluids were prepared of the same composition as 

 those used by Kriiger* in his experiments with Chlorella protothecoides 

 and Chlorothecium saccharophilum. 



* Kriiger, Zopf's ' Beitriige z. Plijs. u. Morph. 2ued. Org.,' Leipzig, vol. 4, 

 p. 103. 



