110 EAMANAN : ON THE HABITS OF AMPULLARIA. 



water, opens the aperture in the roof of the mantle-cavity, repeats all the 

 processes above-noted, and thus prepares itself for breathing air, only still 

 later to reduce the diameter of the orifice in a few minutes and lower down 

 the siphon to respire water. This alternation of aerial and aquatic res- 

 piration takes place for from 11 to 12 minutes at the surface of the water, 

 and finally, the animal closes its operculum and sinks to the bottom. 



At the surface of the water, alternate respiration is not always the rule. 

 The animal may indulge in aerial respiration alone, to a complete exclusion 

 of aquatic breathing. Altogether three modes of respiration can be recog- 

 nised in the animal's life-habits. They are (i) complete aquatic respiration 

 when the animal is under water ; (ii) complete aerial respiration when it 

 is on land ; (iii) rapid alternation of water breathing and air-breathing when 

 it is at the surface of the water. And it is common to find it also (i) at the 

 bottom of the water, without any breathing ; (ii) on land, without any 

 breathing; (iii) at the surface of the water, either breathing air alone, or 

 water alone, or doing no respiration. In these cases of non-breathing, the 

 animal feigns death for a few minutes, sometimes a few hours even, and 

 then resumes respiration. 



When the animal is in its usual surroundings, the following may be 

 taken to be the normal cycle of its movements for purposes of respiration : — 



On the Bottom.'^' — The animal lazily crawling and indulging in 

 aquatic respiration, 5 minutes. 



In Midwater."" — Vigorously crawling to reach the top. Aquatic 

 respiration, 3 minutes, 3 seconds. 



At the Top."' — Alternation of aerial and aquatic respiration, Hi 

 minutes. 6 aerial respirations at H minutes each. 6 aquatic respira- 

 tions at 25 seconds each, falling to the bottom after closing its operculum *^' 

 2 seconds. 



Of the above observations, some are not in agreement with Semper's, 

 while a few others do not fit in with those of Bouvier and Fischer, who, how- 

 ever, were working with a different species of Ampullaria {A. insulorum, 

 d'Orb.). that has its home in the Malay Archipelago and elsewhere. 



Being decidedlyAmphibian in its habits, the animal is occasionally found 

 taking short trips to the land, away from the watery surroundings. It is 

 sometimes unwilling to return to the water for days together. On its 



5. When on the bottom, the animal may occasionally be found at rest with its operculum shut for 

 hours, and sometimes for days together. Whether respiration is goin<^ on in any latent fashion or is 

 temporarily suspended at that time, it is impossible to say. The oxygen stored up in the pulraonar^' 

 cavity might perhaps be then !-ufficient for the low metabolism. 



But when crawling on the bottom, bubbles of gas sometimes collect round the siphonal edge. 

 These may either be carbonic acid gas given off by the lung or the branchial sac, or the atmospheric 

 air retained in the pallial cavity for pneumatic purposes. The siphonal aperture is of moderate size 

 and uniform in shape. 



6. 3 minutes and 3 seconds is the time it takes for getting up my aquarium, whicli measures 

 1 foot and 2j inches high. 



7. When the animal indulges in complete aerial respiration at the surface of the water, the 

 siphonal edge can often be seen contracting and expanding rhythmically and sometimes lying in a 

 tmif'iiiiily extended state f^ir minutes together. This contraction and expansion may correspond to 

 the expiratory and inspiratory processes of respiration. 



8. Instead of sinking, it may occasionally crawl down. 



