parasitic ivithin recent Madreporaria. 241 



Silurian rocks*, filled more or less with the fossilized vegetable matters, 

 the cell-wall being even preserved in the Tertiary forms. 



List of Species of Corals examined. 



Cart/ophyllia clavus, Scacchi, rar. borealis and var. Smithi, Range of specimens, 

 low spring-tide to 90 fathoms. 

 ■\FIabellum laciniatum, Eclw. & H. 380 fathoms. 

 ■\LopJioheHa 2)rolifcra, Pallas. 90 to 422 fathoms. 

 XSoIcnosmilia variabilis, Dune. 1095 fathoms. 

 %BalanophyIlia verrucaria, Pallas. Littoral. 

 \Millepora alcicornis, Forsk. Littoral. 



III. Method of Investigation. 



The parasitic growths which occur in the dense sclerenchj^ma of the 

 Madreporaria are best seen by examining thin transverse and longitudinal 

 sections of recently dead corals, and also by submittiug whole or parts of 

 specimens to the action of very cUlute hydrochloric acid and thus obtaining 

 the remains of the organisms. The upper parts of the corals, which are 

 covered with the soft tissues just before death, are comparatively free 

 from the ravages of the destructive tube-matters ; but the lower portions 

 of the corallum (which have, especially in species with endotheca, been long 

 uncovered by living tissue) are usually crowded with the borings of the 

 parasites. Age and the length of time which has elapsed since the 

 removal of the corals from the sea have no influence on the preservation 

 of the canals bored within ; for they may be traced in fossil specimens, 

 and also in recent forms which have been half a century or more out of 

 the sea. Moreover, so lasting is the peculiar organic basis on which the 

 parasite depends and in and about which the granules and spicula of car- 

 bonate of lime are deposited during coral-growth, that it may be extracted 

 more or less perfectly by weak acids from the oldest corallites which have 

 not undergone fossilization ; and in the instances of some mid-Tertiary 

 reef-building forms I found it to be distinguishable. The most com- 

 plete organic films are to be obtained from corals recently dead. The 

 continued preservation of the vegetable cell-wall and its cytioplasm 

 appears to depend upon the same causes which determine that of 

 the organic film. Sometimes the delicate tubular cell- wall may be 

 traced, in old specimens decalcified, amidst the organic matter ; and I 

 have noted its preservation in a Miocene coral ^ as a transparent and 

 probably mineralized structure ; but usually age appears to affect the 

 cell-wall, which is commonly found in a very indifferent condition and 

 more or less imperfect in old and dry specimens. In some fossils the 

 spores, either oospores or conidia, are found in a wonderful state of pre- 



* P. M. Duncan, Proc. Geol. Soc. (abstract of communication) for Jan. 19, 1876. 

 t From the J^orth Atlantic. \ From the Spanish coast. 



§ From own aquarium, [| From Bermuda, 



^ Quart. Journ. Geol. Soc. 



