62 THE PROTOZOA 



C. SOME ECONOMIC ASPECTS OF THE PROTOZOA 



The Protozoa are frequently objectionable because of the appear- 

 ances, odors, and tastes which they may impart to water. In the sea 

 great areas may be colored orange, red, etc., by incalculable numbers of 

 Noctiluca or Dinoflagellidia {Prorocentrum, Glenodiniiim), while at 

 night their presence is indicated by brilliant phosphorescence, the 

 light being due to the rapid oxidization of a substance created by the 

 organisms and thrown out by them upon irritation. In Puget Sound 

 and in Alaska I have seen hundreds of acres of the sea surface 

 colored orange by Noctiluca miliaris, although the single individuals 

 are less than one-fiftieth part of an inch in diameter, and Haeckel 

 ('90) graphically compares such masses to " tomato soup " ! When 

 Protozoa occur in great numbers in fresh water, and especially in 

 drinking water, they may cause considerable annoyance ; for by the 

 color, odor, and taste which they impart they render the water unfit 

 to drink. The colors are due in the main to the Phytoflagellida, and 

 only those forms which are capable of making their own food are able 

 to live in pure drinking waters. The most frequent causes of trouble 

 in this respect are Uroglena, Peridinium, or its allies, Euglena and 

 other Euglenoids, and Synura, all of which are flagellates. The 

 odors and tastes, however, are more offensive than the colors, and as 

 they are frequently misunderstood and regarded as evidence of pollu- 

 tion, an explanation may not be out of place. Ehrenberg noticed 

 that certain flagellates (Chlamydomonas pulvisculus and Chlorogoniimi) 

 impart a certain oily odor. Dunal ('38) and Joly ('40) described an 

 odor like that of violets from the masses of Hcematococcus which gave 

 to a portion of the Mediterranean a distinct red color. The Massa- 

 chusetts State Board of Health, dealing with this problem of the 

 drinking waters, have obtained important results in this direction. 

 They have shown that certain of these organisms may have definite 

 and specific odors which, like the odors of flowers, can be recognized. 

 An "oily odor" was traced to Synura and Uroglena, an "Iceland 

 moss" odor to Peridinium, a "violet odor" to certain Euglenoids, 

 etc. 1 The cause of these odors has been the subject of a number of 

 investigations, and it has been found that they are " living odors " due 

 to disintegration of the cells rather than to their decomposition, a view 

 first advanced, I believe, by Butschli ('84), who described a highly 

 characteristic "fishy odor" from Euglena sanguinea, while the cells 

 were found to be disintegrated, although not decomposed. The 

 matter was considered more extensively by the writer ('92), who found 

 that in waters infested with colonies of Uroglena amcricana the odor 

 was not developed until the organisms had passed through the water 



!See S. B. II. ('92). 



