38 



THE CHICAGO ACADEMY OF SCIENCES. 



TABLE VII. 

 Intervals between the breathing spells of Lymnaens palustris. 



- 

 o 



Time Under Observation. 











— - 



— — 



S§ 



July 5 

 335 



Min. 



July 6 

 300 

 Min. 



July 7 

 125 

 Min. 



July 8 



90 

 Min. 



July 11 

 220 

 Min. 



July 12 

 140 



Min. 



- = - 



- -- 



- . - 



- '■ = 



- i - 

 = gja 



sis 



= - 

 2 % 



u 



- - 

 5 jb 



i 



1 



1 



o 



B 







3 



9 



10 



32 



B25 





27 



2 



11 



4 



7 



2 



4 



5 



33 



1215 





•J7 



3 



19 







2 



2 



3 



3 



27 



1215 





42 



4 



26 



26 



9 



3 



6 



6 



76 



1215 





16 



5 



45 



3 



3 









51 



760 





15 



36 











13 



16 



29 



360 





12 



36 











3 



1 



4 



360 





9 



37 





10 



5 



8 



12 



3 



38 



880 





23 



38 











8 



7 



15 



360 





25 



39 











7 



7 



14 



360 





26 



40 







18 



7 







25 



215 





9 



41 







14 



5 







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 

 respirator}- 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. Xo. 4, Table VII, whose average interval was 16 

 seconds, kept the respiratory tube open noticeably longer than any 

 other snail — 10 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 Lymnaeas 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- 



