Practical Course. 87 
DISSECTION OF THE SNAIL. ? 
Large snails are not easily obtainable in Dehra, though small ones are 
common enough, There is a large land species (Achatina fulica, Ferussac) 
which is common in Caleutta and which does very well for dissection. It is 
known locally as ghonga. The snails should be killed by drowniug them, 
as -by this means they are obtained in an expanded condition. They should 
be allowed to remain in the water for about two days, after which they 
can be preservéd in alcohol until wanted for dissection. 
Examine a specimen and notice— 
(1) The coiled shell set on the animal’s back, with-its apex point- 
ing to the right side. 
(2) The expanded fleshy foot upon which the snail progresses. 
(8) The head in front, which bears two pairs of tentacles. The large 
upper tentacles each terminate in an eye, which can only 
be seen when the tentacle is fully expanded. 
(4) The mouth, which is a large median opening in front of the 
head, closed by large fleshy lips. 
(5) The pédal gland, which opens in a large median hole beneath 
the mouth. Stick a match into the opening of the pedal 
gland and feel how far it goes back into the substance of 
the foot. 
{6) The genital opening. This is a small round hole which lies on 
the right side, a little behind and below the upper tentacle. 
From it the ova and spermatozoa are extruded at different 
times of the year. 
(7) The large oyening of the pulmonary.chamber. It lies on the 
right side, just where the shell meets the back, Stick 
a match into it and feel the extent of the large pul- 
" monary chamber which lies inside the shell, 
Cut and break away the shell carefully so as not to injure the animal. 
Begin from just above the pulmonary opening, and extract the animal 
completely. Notice the transparent membrane which forms the upper 
wall of the large pulmonary chamber. Stick a thin match into the open- 
ing of the pulmonary chamber, and by feeling about in the right hand 
upper comer of if you will be able to make out the anus and Bono 
portion of the digestive tube, which opens in this spot. 
Immerse the specimen in water and arrange the coil as it was when 
inside the shell, Just above where the pUlonaty chamber terminates, 
on the left of the body, is a rounded chamber with transparent walls 
(pericardium) which contains the heart. To the right of it lies the large 
yellowish kidney, which occupies the space between the heart and the 
2 It may be necessary to curtail or omit this dissection for want of time. 
