in which it appeared in the different groups of Medusae, in all this work bringing out the prevailing features of the anatomy in contrast to the individual peculiarities.  He shewed that microscopically all the complicated systems of canals and organs were composed of two “foundation-membranes,” two thin webs of cells, one of which formed the outermost layer of the body, while the inner formed the lining of the stomach and canals in the thinner parts of the body, such as the edges of the umbrella-like disc, and towards the ends of the tentacles.  These thin webs formed practically all the body.  In the thicker parts there was interposed between them an almost structureless layer of jelly, placed like padding between the lining and the cloth of a coat.  He shewed that blood-vessels and blood were absent, in which he has been confirmed by all other observers.  He declared more doubtfully against the existence of a special nervous system, and it was not until long after, when the methods of microscopic investigation were much more perfect, that the delicate nerve-cells and nerve-fibres, which we now know to exist, were discovered.

Having thus shewn the peculiar organisation of the group he turned to seek out its allies among other families.  The Medusae consisted essentially of two membranes inclosing a variously shaped cavity inasmuch as all its organs were so composed.  The generative organs were external, being variously developed processes of the two membranes.  The peculiar organs called thread-cells—­poisoned darts by the discharge of which prey could be paralysed—­were universally present.  What other families presented these peculiarities?

There are to be found abundantly in sea-water, and less frequently in fresh water, innumerable forms of animal life called Zooephytes or animal plants because they occur as encrusting masses like lichens, or branched forests like moss, on the surface of stones and shells.  A common habit gave this set of creatures their common name; but, although they were grouped together, there was no greater affinity among them than there is racial affinity among people who clothe themselves for an evening party in the same conventional dress.  Huxley examined a large number of these, and picked out from them two great families of polyps, the Hydroid and Sertularian polyps, which each consist of colonies of creatures very much like the little fresh-water hydra.  He shewed that the tubular body of these and the ring of tentacles surrounding the mouth were composed of the same two foundation-membranes of which all the organs of Medusae are composed.  He found in them the poisoned arrows or thread-cells of the Medusae, and the same external position of the reproductive organs.  And, lastly, he separated from all other creatures, and associated with his new group, some of the strangest and most beautiful animals of the tropic seas, known to science as the Physophoridae and the Diphyidae.  The best-known