parasitic within recent Madreporaria. 



257 



Fig. 52. A large filament close to the entry of the Aclilya, with conidia-like masses in 



the cytioplasm. X 400 diameters. 

 Fig. 53. A tubular filament ending and having numerous ovoid bodies close to t'le 



cell-wall (zoospores). X (300 diameters. 

 Fig. 54. Interlaminar tubes of Achlya crowded with cytioplasm. X 400 diameters. 

 (See figs. 33-35.) 



Fig. 55. Zoospores sending out filaments when within the parent filament. X 600 



diameters. 

 Fig. 56. A filament like fig. 53. 

 Fig. 57. A typical filament of Achlya 'penetrans. 



Figs. 58-60. Endings of filaments with dissepiments and granules, x 400 diamete/s. 

 Fig. 61. Zoospores, non-ciliated. X 600 diameters (high eyepiece). 



Appendix to a Communication on Thallophytes in Recent Corals. 

 By. Professor Duncan, F.R.S. &c. Received May 11, 1876. 



Since my essay on the Thallophytes in Recent Corals has been sent to 

 the Royal Society, I have become aware, after the examination of somi 

 deep-sea corals (depth 363 fathoms), that thread-like dark green organ- 

 isms of a vegetable nature ramify on their surface and penetrate it. 

 These filiform organisms are visible to the naked eye, and, when examined 

 under the microscope, are shown to be unicellular and to contain green 

 colouring-matter. They leave linear depressions on the surface of the 

 coral which correspond with them in diamater and outline, and they 

 penetrate and dip under the surface sometimes to reappear above. Their 

 course may often be traced in AmphUielia oculata just balow the surface 

 without a high maguifying-power being usad. From the stain which is 

 often seen on the coral on either side of these superficial filamentous 

 organisms, it would appear that they are sometimes broad ; but the 

 excavating filaments do not appear to have been broader than they were 

 when they first penetrated or covered the corallum. I have traced the 

 ramifications of these large filaments within the coral by dissolving in 

 weak hydrochloric acid, and they resemble those described by me. They 

 appear to be the same as those which are found in the interlamellar 

 tissue of the septa, and the difference is only in size. 



Having had the opportunity of examining some large Foraminifera 

 from the Indian Ocean, I can testify to the presence in them of multi- 

 tudes of small Scqjrolegnia-lookmg filaments, but which, like those 

 described by Mr. Moseley, have green contents. 



Finally, I have lately discovered that, besides the penetrating planta 

 and spongida of corals, there are long tubular organisms which end in 

 bag-like terminations so greatly resembhng some of the calycles of 

 Hydroida that they demand careful investigation. These filaments 

 penetrate and also exist in the previous channels of Clioua. 



