. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STUDIES IN ANIMAL AGGREGATIONS. 303 TABLE I. SHOWING THE RESULTS OF EXPOSURE TO SUSPENSIONS OF COLLOIDAL SILVER FOLLOWED BY TRANSFER TO WATER SIMILAR TO THAT TO WHICH THE ANIMALS WERE ACCUSTOMED. All were run at room temperature. Drops Num- Time Animal. Cc. of Water. Col- loidal ber Ani- Exposed Colloidal Sur- vive. Mov- ing. Died. Silver. mals. Silver. Planaria maculala. . IS 12 6(3) 2 hrs. ii 2 7 15 12 i(75) 2 hrs. 72 66 3 5 i 5(3) 26 hrs. 9 0 6 5 i 1(25) 26 hrs. 25 23 o Planaria dorotocephala 10 2 40(1) 7 hrs. i s i 2=; 1
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STUDIES IN ANIMAL AGGREGATIONS. 303 TABLE I. SHOWING THE RESULTS OF EXPOSURE TO SUSPENSIONS OF COLLOIDAL SILVER FOLLOWED BY TRANSFER TO WATER SIMILAR TO THAT TO WHICH THE ANIMALS WERE ACCUSTOMED. All were run at room temperature. Drops Num- Time Animal. Cc. of Water. Col- loidal ber Ani- Exposed Colloidal Sur- vive. Mov- ing. Died. Silver. mals. Silver. Planaria maculala. . IS 12 6(3) 2 hrs. ii 2 7 15 12 i(75) 2 hrs. 72 66 3 5 i 5(3) 26 hrs. 9 0 6 5 i 1(25) 26 hrs. 25 23 o Planaria dorotocephala 10 2 40(1) 7 hrs. i s i 2=; 10 2 3(25) 7 hrs. 75 63 0 Dendrocoelum lacteum c I 5(3) 26 hrs. -i i 12 5 I 1(24) 26 hrs. 18 1 8 6 Ophioderma Righted mean time brei'ispina. SO 2 48(1) —16 hrs. 41 30 mm. o 50 2 12(5) hrs. 59 38 sec. o More cases with different concentrations could be given but the result is the same in all. This agrees entirely with the expe- rience of Drzewina and Bohn, who used a wide range of animals; and with that of Bresslau, using different toxic reagents with ciliates. A priori one would expect exactly such a result since in each case there is much less of the toxic substance present per indi- vidual composing the larger groups, than when 1-3 animals are placed in the same amount of the same concentration of toxic substance (Pieron, 1921). Yet the possible menace of crowding, so frequently given as the only result of confining many animals within a small space, may easily be demonstrated even here. With the Ophioderma, for example, if the glass fingerbowls were cov- ered with glass plates during the exposure to colloidal silver, thus stopping free gaseous exchange, the grouped animals were in much worse condition than were their isolated fellows. CAUSE OF GROUP IMMUNITY. When one begins to inquire into the causes of the greater im- munity of the grouped individuals, he immediately finds division. RY - •. _''-*•. Please note that these images are extracted from scanned p
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
