of Australian sponges.  With a passing reference to some peculiarities of the lower marine animals of the Australian coast, Dr. Ledenfeld remarked upon the preponderance of sponges over other forms of marine life in that part of the world.  It has long been a point of discussion as to whether sponges belong to the vegetable or animal kingdom, but naturalists are now generally agreed in regarding them as animals, a conclusion, the lecturer remarked, that Aristotle had also arrived at.

Sponges grow in a variety of more or less irregular shapes, but it has been observed that the most regular structures occur in the calcareous species.  As to color, Dr. Ledenfeld remarked that some of the Australian sponges are of exceptionally brilliant hues, while others range from the black of the common sponge (Euspongia officinalis) to a pure white.  Also, it may be remarked, the sponges growing in deep water are of less decided color and more elastic in character than those living in shallow water, and from the last named quality are more valuable in commerce.  The irregular honeycombed appearance of the sponge is due to a most complicated canal system, consisting of a series of chambers through which the water is drawn by the animal in always the same direction.

The inhalent pores are very minute, and open into small subdermal cavities which communicate by means of interradial tubes with the ciliated chambers, the latter being very small ramifications of the interradial channels, and in them the movement causing the current of water is maintained.  From hence all faecal and other matter is discharged through the oscula, the larger openings observed on the surface of the sponge.  Dr. Ledenfeld showed the different parts of sponges by means of microscopic slides thrown on to a screen, and also the shape and arrangement of the chambers in different species.  The ciliated chambers especially attracted attention.  They are very small and circular, and the interior is clothed with cells very similar to the cilia cells in higher animal life.

These cells are arranged around the ciliated chambers in the form of a collar, and from each cell flagella protrude, which are in continual motion.  These flagella, like bats’ wings, are capable of being bent in only one direction, so that, in the course of their pendulum-like motion, in the movement one way the flagella are bent, while in the return movement they remain stiff, thus causing a current of water always flowing in one and the same direction.  These ciliated chambers are easily detected in the sponge by means of a microscope, as they appear more highly colored.  After the lecturer had thus given a general outline of the structure of the sponge, he drew attention to the character of its food and its method of digestion.  It is not known exactly what the sponge lives upon, but if upon other animals they must be necessarily very small, owing to the size of its inhalent pores.