Pond life / by Edward C. Ash.

  • Edward C. Ash
Date:
[1913]
Catalogue details

Licence: In copyright

Credit: Pond life / by Edward C. Ash. Source: Wellcome Collection.

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    remarkable that this family is more in evidence than any other, for we can only presume that the more the arms the more the food. Plumatella repens, the most common variety of this family, has egg-shaped statoblasts. Lophophore, although not so common, rejoices in the fact that it is the only species of its kind. The Polypides are enclosed in a jelly-like glassy case. As the colony increases in age it alters, becomes segmented, the holes more deeply cleft, until, as one would expect, separa- tion takes place. The divided part floats away to lay the foundations of a subsequent colony. Lophophore has the power of movement, and is able to wander to its “ heart’s ” desire. Compared with the immobile condition of Plumatella and many others, such freedom seems “ too good to be true.” Lophophore is no lover of excessive exercise, and its travels, although of long duration, are not of great distance—half an inch is usually the maximum. The undertaking of so great an enterprise takes twenty-four or more hours to accomplish. Cristatella Mucedo is the great traveller amongst the Polyzoa ; in fact it is especially equipped for a wandering life. The outer' case has a flattened sole, on which the creature moves. On the upper surface the colonists protrude their plumes, seemingly perfectly contented in whatsoever direction the foot is taking them. It is interesting to know that the base of the colony pro- duces a thin film that oils the surface on which the creatures are moving. Thus friction is minimised, and should the direction lead downhill, and the colonists at the same time be energetically waving, it is quite easy to follow what must necessarily occur. On levels and uphill, if Cristatella does walk uphill, matters are different. If the foot oils the surface, it is doubtful whether the creature would be able to advance in the latter case, but on the level, by reason of certain altera- tions of the under surface of the sole, a slow movement would easily result. It is peculiar that the movement is always in the direction of the longer axis, and never sideways. This fact would seem to denote that some of the creatures are responsible for the steering, so that the direction is not a matter of mere chance, as one is given to suppose. Colonies of Cristatella mucedo are often as much as 4 to 5 inches long, but very narrow, as although the colony is continually increas- ing in length, yet the breadth does not. As time goes on some of the community die, but no alterations are made, so that the living and the dead remain together. In fact it
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