Examination of Calceola sandalina.—In the Calceola examined the tubes of all kinds were seen and conidia of globular shape included in the larger ones. The largest tubes (fig. 12) are four or five times as broad as the medium-sized straight tubes (fig. 11); and their exit in a loculus opening outwards at the surface can be seen. The loculus (figs. 12 & 13) sometimes contains a crowd of spores; and little wavy canals pass out from all sides. The contents of the tubes have undergone alteration in some, and a reddish tint has replaced the ordinary greenish-black colour.
The sections of such fossils necessarily contain tubes at different angles; and some which lie parallel to the line of incision are injured; hence the continuity of the conidium-bearing tubes is interfered with, and these are often left without a trace of the former tube. The same occurs with regard to the small branching tubes, which become broken up and isolated by the section. This is seen in a Lower Silurian Foraminifer (fig. 5).
Remarks.
A comparison of the parasitic excavations of recent corals with those of the Secondary and Palæozoic ages presents most remarkable resemblances. Tube may be compared with tube in all its parts; but fossilization has produced appearances in the spores and conidia which suggest distinction between the recent and the fossil kinds of Algæ. Nevertheless the general character of the re- productive resting spores and the conidia arising from the vegetative part of the organism remain much the same. The large tubes in the palæozoic coral and Brachiopod, or whatever else Calceola may be, would at first sight indicate a different species of parasite from those which formed the smaller penetrations; but both large and medium-sized tubes often exist in the same recent corallum, and these last now and then give off others so small and so finely linear that their diameter cannot be measured. Whilst recognizing two or three forms of parasitic Algæ within these sclerenchymatous structures of recent and ancient date, it does not follow that they are to be made into different species. They may all be parts of the same mycelium- like growth of the parasite, and may depend upon the nature of the nidus in which growth has taken place.
Tubes of analogous sizes and shapes are found together in recent corals, and they are often continuous.
Wedl suggested that the Conferva which grew into the shells was Saprolegnia ferax. Kützing and Kölliker, from the want of cell-like partitions in the tubes, objected to the confervoid nature of the parasite, and urged that it is one of the Fungi—one of a group which grows at the expense of animal tissues, and secretes carbonic anhydride.
The distinction between Saprolegnia and the Fungi, however, is but doubtful. Its spores vegetate; and the tube growing from them, in some species, speedily perforates Confervæ and dives into their cells, growing and developing at their cost. It is really in-
