Hooke, whom we mentioned in our chapter on the History of the Microscope, though a careful observer, was quite misled by the sea-mat; he thought it was a seaweed, for he wrote: “I have not, among all plants and vegetables I have yet observed, seen any one comparable to this seaweed. It is a plant which grows upon the rocks under water and increases and spreads itself into a great tuft, which is not only handsomely branched into several leaves, but the whole surface is covered over with a most curious knot of carved work, which consists of a texture much resembling a honeycomb, for the whole surface on both sides is covered over with a multitude of very small holes, being no larger than so many holes made with a pin, and ranged in the neatest and most delicate order imaginable, they being placed in the manner of a quincunx, or very much like the rows of eyes of a fly, the rows or orders being very regular which way soever they are observed. These little holes, which to the eye look round, when magnified, appear very regularly shaped holes, representing almost the shape of a round-toed shoe, the hinder part of each being, as it were, turned in, or covered by the toe of the next below it. These holes seemed walled about with very thin and transparent substance, looking of a pale straw colour, from the edge of which, against the middle of each hole, were sprouted out four small, transparent, straw-coloured thorns, which seemed to protect and cover those cavities.” As a well-known author has remarked: “This is really a wonderfully faithful description of the common sea-mat, and one cannot help picturing the surprise and delight of old author Hooke, could he have seen a portion of a living colony under a modern microscope.” One of our finds may be the “Bird’s head.” It is a branched form, quite unlike the sea-mat but it is of even greater interest. Under the microscope, we shall see the many waving tentacles, but another feature is sure to attract our attention, a feature which is responsible for the popular name of the colony. On the outside of each cavity containing a member of the colony there is a structure which resembles nothing so much as a hawk-like bird’s head atop of a long neck. While the tentacles wave in the water, the bird’s head snaps vigorously, moved here and moved there. The birds’ heads, which might be mistaken for parasites stealing food from the waving tentacles, really perform the useful function of keeping them clean and warding off creatures which might do them harm. [Illustration: _By the courtesy of Messrs. F. Davidson & Co._ 1. A SECTION OF HUMAN SKIN The corkscrew-like pores, leading from the sweat glands to the surface, are plainly seen in the section. 2. THE FACE OF A FLY A wonderful photograph, at 15 inches, taken by the micro-telescope. Notice the very large size of the eyes relative to the rest of the head. ]