38 THE CHICAGO ACADEMY OF SCIENCES. 
TABLE ‘VII. 
Intervals between the breathing spells of Lymne@us palustris. 


4 Time Under Observation. 
2 See ce g 
ao July 5 July 6 July 7 July8 | Julyll | Julyi2 | pox ae gas 
=e 335 300 125 90 220 140 2nV mH SP 
58 Min. Min. Min. Min. Min. Min. | 38° 22 aaa 
we ASS HO <84 
it 2 8 0 3 9 10 32 825 27 
2 alae 4 tf 2 4 33 1215 37 
3 19 0 2 2 3 3 27 1215 42 
4 26 26 9 3 6 6 76 1215 16 
S 45 3 3 51 760 15 
36 138 16 29 360 12 
36 ste 3 1 4 360 9 
31 10 5 8 12 3 38 880 23 
38 8 7 15 360 25 
39 ae i 7 a 14 360 26 
40 18 7 ais ie 25 215 9 
41 
14 5 Bi ae 19 215 11 
“The amount of atmopsheric air taken in by any individual dur- 
ing 24+ hours depends not so much on the number of times it opens its 
respiratory tube at the surface as upon the length of time the tube re- 
mains open for inhalation. In this particular the 12 snails under obser- 
vation exhibited decided individuality, some keeping the tube open only 
a fraction of a second, while others extended the period of inhalation 
even to 96 seconds. No. 4, Table VII, whose average interval was 16 
seconds, kept the respiratory tube open noticeably longer than any 
other snail—40 and 50 seconds being its usual length of time, and 96 
seconds the limit, while the average time of inhalation for the other 
snails was about 15 seconds.” 
Many Lymneeas have been observed to breathe without coming to 
the surface, and such respiration is considered abnormal. Pauly di- 
vides these abnormal breathers into three classes, as follows: 
1.—Abyssal snails which cannot possibly reach the surface. 
2.—Snails which make no attempt to reach the air though living 
in shallow water. 
3.—Snails artificially restrained from securing atmospheric air. 
The first class has already been discussed (see under bathymet- 
rical range). Pauly cites a number of examples in which the animals 
secured air without visiting the surface of the water, and he explains 
as the reason for this change of habit, the ability of the snails to se- 
