PARASITIC WITHIN SILURIAN AND TLRIIARY CORALS. 209 



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 Palaeozoic ages presents most remark- 

 able 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 AlgaB. 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 palaeozoic 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. AYhilst recognizing two or three 

 forms of parasitic Alga? 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. Kiitzing and Kolliker, 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 Confervse and dives into 

 their cells, growing and developing at their cost. It is really in- 



