A tentacle is a flexible limb used to either move an animal around or as a sensor, i.e. for smelling or seeing. A snail sees through the two longer, higher up tentacles and they can move them around separately to get a better view of its surroundings. It is important for them to be able to move their eyes around because they can't change how their eyes are focused as they do not have the cilia muscle. There is a very small black dot at the end of each tentacle which is the eye. Snails do have good eye sight; however they cannot see colours.
The two tentacles below these point downwards, tracing along the floor, and are used to smell to give the snail an idea of its environment and to help it find food. A snail's sense of smell is very important as they have no ears and therefore cannot hear. These tentacles also help the snail find a partner as they let off olfactory hormones which attract mates.
A snail can retract its tentacles quickly if they touch an object or surface and they are controlled separately. The snail retracts each eye using a retractor, which is the muscles marked at 2 and 4 on the diagram above. When the muscles retracts the eye is pulled inside the tentacle and hidden; however depending on how transparent the snail's tentacles are, you may be able to see the eye going up and down, seen as a black spot. If the snail wants to extend its tentacle then it must project blood fluid into it, as showing with label 3.
Above is a close-up of a land snail's tentacle. The snail that I will be using in my hybrid will have the same characteristics as this tentacle because they're both land snails; however the colouring may be different and so the visibility of the eye may not be as great. The texture of the stem of the tentacle looks slightly slimy, with almost a bubbly texture. The skin doesn't look rough, but it just looks like it has small, smooth bumps. The texture almost reminds me or an orange skin or if someone took a very closeup shot of some water bubbling. The colouring is a very light green, however it look very transparent so this colouring may change with different lighting and backgrounds. The tip of the tentacle looks very smooth and shiny, possibly with slime. This look very transparent as you can see the retractor muscle underneath the layer of skin. The tip of the tentacle looks like an extension of the tentacle on the top, keeping in a smooth line, however the bottom looks like it is sagging down slightly. The bottom part of the tip of the tentacle almost looks like a raindrop before it separates and falls. You can see a black dot at the very end of the tentacle and you can see that it causes the tiniest bit of a protruding dent, so it's not a perfectly round ball on the end.
The above photo shows how the tentacles are connected to the slug's head. There are lumps all over the snails head, these lumps get smaller and smaller as they travel up the tentacles and this is how they are blended into the skin. The tentacles can go up at quite sharp angles, but they are always blended into the skin on the head with the continuous lumps.
Resources:
NORDSIECK, R., 2015. The Living World of Molluscs [7 November 2015]. Available from: http://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/tentacles.html
Goldsmith, O., 1990. The Illustrated History Of The Natural World. New York: Arch Cape Press
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