Methodological guidelines on tasks


PORIFERA.

Cells not differentiated to form definite organs. Water admitted through surface pores and ejected through an osculum or through oscula.

CLASS 1. Calcarea.

With a skeleton composed of calcareous spicules.

  1. Examine a dry specimen and notice its general shape, manner of attachment, and osculum. The osculum is surrounded by a funnel of rather long spicules. Distributed over the general surface, more or less hidden by the numerous spicules, are many small pores. Their presence may be demonstrated more satisfactorily later.
  2. Look for indications of budding. If your specimen does not show this, examine others. Make an enlarged drawing of a sponge.
  3. Many apopyles, the inner openings of tubes that are embedded in the walls of the sponge, will be seen opening into the cloaca. Are the apopyles arranged in any order?
  4. With the low power of your microscope (with the light turned off) examine the cut wall and find that it is traversed by parallel tubes. Determine that these tubes are of two kinds.
  5. Regular, nearly cylindrical tubes that open into the cloaca through the apopyles and that bear tufts of spicules on their closed ends, at the surface of the body. These are the radial canals. It is frequently hard to see their openings into the cloaca, as the apopyles are narrow, so the section only occasionally passes through them.
  6. Smaller and less regular tubes that open on the outer surface between the clusters of spicules, and do not open into the cloaca. These are the incurrent canals. In life there are small pores, prosopyles, that open from the incurrent canals into the radial canals. These openings are very minute and are apparently capable of being closed. They are never visible in dried material.
  7. Examine thin, transverse sections of a dry sponge and determine the positions of radial and incurrent canals. Make a drawing that will show the arrangement of the canals.
  8. Examine the spicules and determine their positions as regards canals. Boil a portion of a sponge in caustic potash until only the spicules remain and examine the spicules. See if more than one kind occurs.