238 



Prof. P. M. Duncan on Thallophytes 



" On some Tliallophytes parasitic within recent Madreporaria/^ 

 By P. Martin Duncan_, M.B. Lond.^ President of the Geolo- 

 gical Society, F.R.S., &c. Eeceived March 17, 1876-^. 



[Plates 5, 6, 7.] 

 Contexts. 



I. A Notice of the Discoyeries of previous Observers. 

 II. The Eauge of the Parasites in living Corals. The Age of the fossil forms. 



List of species of Madreporaria examined. 

 III. Method of Investigation. 



lY. The usual appearances of typical Parasitic Canals, 

 y. The Parasitic Canals near the exterior and their Methods of entry : Eepro- 

 ductive Elements. 



VI. The large confervoid-looking Filaments within the Organic Basis of the Corals. 

 VII. Method of Entry and Growth of the AcMya. 

 VIII. Structure of Eeproductive Elements and Classificatory Position. 

 IX. On the Occurrence of Aclilya {Sairrolegviia) ferax, Ktz., in Caryophyllia 



Smithi. \ 

 X. Summar5^ 



Explanation of the Plates. 

 Appendix. 



I. A Kotice of the Discoveries of previous Observers. 



During some iiiTestigations into the nature o£ the sclerenchyma of the 

 Stony Corals (Madreporaria) I Tvas impressed with the importance of 

 examining the method of entry, growth, and distribution of the miimte 

 unicellular parasite which so constantly penetrates and ramifies in minute 

 tubular excarations in the sohd structures. 



The interest of the subject struck Quehett in 1851 ; for he described 

 the mumte tubules of a parasite in his Lectures, which he subsequently 

 published in 1854. He wrote as follows : — " Confervoid growths are 

 also Tery frequently met with in the skeleton of corals, as aU those bodies 

 possess animal matter, which, decomposing after death, becomes a nidus 

 for the development of Confervae ; and hardly a section can be examined 

 without exhibiting such an appearance as shown in fig. 78 "t. This 

 figure exhibits almost straight canals, of great tenuity and of different 

 lengths, cutting across the normal structures at different angles. 



Before this time. Carpenter j: and Bowerbank§ had shown that 

 molluscous shells contained tubular structures ; and Quekett, in his 

 work, agreed "^^ith them as regards their facts ; but he beheved (as, 

 indeed, Carpenter did also at that time) that, whilst some of the tubules 



* Eead May 11, 1876. See ante, p. 17. 



t John Quekett, 'Lectures on Histology,' vol. ii. p. 153 (185-1). 



\ Carpenter, in Todd's ' Cyclop£edia of Anatomy and Physiology,' article " Sliell," 

 vol. iv. p. 562 (1852); Ann. & Mag. Xat. Hist. Dec. 1843; Eeport^Brit. Assoc. 1844, 

 1847. 



§ Bowerbank, Trans. Microsc, Soc. i. (1844). 



