OF ARTS AND SCIENCES. 179 



of the Cochituate water attracted public notice ; when I called the 

 attention of one of the chemists employed to analyze the water to 

 the presence of this oil, and suggested that it might be the cause of 

 the evil. But it did not appear probable to either of us that a small 

 amount of oil could occasion so serious an effect ; and thus the mat- 

 ter rested until the commencement of the present year, when Dr. 

 Hayes placed in my hands for microscopic examination the gelatinous 

 substance collected by him on cloth filters. The microscope revealed 

 an abundance of oily globules in the bodies of the Cyclops and other 

 minute crustaceans, of which the mass on the filter chiefly consisted ; 

 and the source of the oil obtained in his experiments was at once 

 evident. At this time (early in January) very few confervse or other 

 vegetable organisms were found. The empty siliceous shells of vari- 

 ous Diatomaceae were abundant, as usual, but scarcely any specimens 

 were living, or contained organic matter. Yet the peculiar flavor of 

 the water was as strongly marked as in the autumn, when Confervse 

 and other vegetable organisms abounded. 



" The crustaceans in which the oil occurs are several species or 

 varieties of Cyclops and Daphnia, and probably other allied genera 

 of the division Entomostraca. In the living animals, the oil is clearly 

 seen, by the aid of the microscope, through the carapace, which is 

 mostly transparent ; and is distinguished by its high refractive power, 

 and other optical characters, from the other contents of the shell. It 

 can also be extracted by ether, and still more satisfactorily by strong 

 alcohol, from the body of the animal, while in the field of the micro- 

 scope. The quantity present is exceedingly variable, not only at 

 different times, but in different individuals collected at the same time. 

 In a few specimens no globules are visible. In others, they are so 

 abundant that the oil forms at least one quarter part of the bulk of 

 the animal. These large quantities occur only in the Cyclops, which 

 is by far the most abundant form present ; the other crustaceans con- 

 tain much less. 



" Its distribution in the body of the animal is remarkable, being 

 diffused irregularly in globules of various sizes (usually spherical and 

 occasionally ovoid or pear-shaped), and in masses formed by the 

 coalescence of globules ; and it appears to have no definite connec- 

 tion with the internal organs of the animal. Sometimes small globules 

 are seen, even in the last joints of the tail. No sac or envelope is vis- 

 ible around them, as they occur in the animal, or when liberated by 



