On the behaviour ofSabella

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Abstract
In S. spallanzanii and in S. pavonina the tube consists of a stiff stem and a more flexible root, and is open at both ends. The opening of the stem (anterior opening) is always well above the substratum. That of the root (posterior opening) was above the surface of the substratum in S. spallanzanii but embedded in the mud in S. pavonina. Both spp. irrigate their tubes vigorously whether the crown is expanded or withdrawn. In S. spallanzanii, pauses are brief and rare; the direction and velocity of irrigation often change and certain characteristic patterns are constantly reproduced. In S. pavonina, there may be pauses of over an hour''s duration and irrigation is tailwards only. The fact that the former sp. irrigates in either direction and the latter in one direction only is clearly correlated with the difference in form of their tubes. As the worms were studied under identical mechanical conditions, the behavior difference is inherent. Decapitation (removal of crown, collar and part or all of the thorax) has very little effect on the irrigation behavior of either sp. This suggests that the crown is unimportant as a respiratory organ. A worm may still be very active, even though its crown is withdrawn into its tube. The suggestion is made that feeding may occur from the irrigation current when the crown is withdrawn.
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