244 



Prof. P. M. Duncan on Thallophytes 



The number of the canals varies also i]i di"fferent specimens, age and 

 bathymetrical range regulating the parasitic growth more or less ; they 

 are more common in the corals with lax textures like the Perforata than 

 in the Aporosa. 



In some of the inner parts of the hard deep-sea corals the canals are 

 few in number and are very long and narrow. These interior canals 

 often give off, either from their whole surface, from parts of it, or only 

 from the swollen parts, loner and very delicate tubes of from ■ to 



. . .. 10,000 / 



^-^^ inch in diameter ; but this appearance, which is very common in 

 such species as Balanophyllia verrucaria and Caryophyllia elavus, var. 

 horealis, is extremely rare in others (Plate 6. figs. 20-28).1 



When parts of corals corresponding to these interior sections and septa 

 are decalcified, a repetition of the appearances of the canals is seen in the 

 arrangement of their contents. Each canal contains and has its interior 

 lined by a homogeneous transparent tubular cell-wall, and this contains 

 fluid and more or less solid contents here and there. 



The cell-wall is continuous through all the ramifications, and ends 

 abruptly in the stunted branches, and it lines the globular ends and all 

 the swellings. It can be traced to give off the extremely delicate 

 tubules to the minutest ramifications just noticed. The cell-wall 

 structure appears to lie against the sclerenchyma of the coral, but 

 not in a perfectly smooth canal ; for there are minute pits and rough- 

 nesses on the inside of the canal, into which the tube itself does not fit 

 (Plate 5. fig. 7, and Plate 7. figs. 56 & 57). 



Cross partitions in these tubular cells are very rarely seen ; and even 

 in the majority of instances in which one might feel disposed to admit 

 their occurrence, it is possible that the dissepiments are more apparent 

 than real, being the result of light passing up between two closely 

 approximated masses of granules (Plate 7. figs. 58-60). 



This coalescing of granules in masses, with spaces between them, is 

 commonly seen ; and a moniliform appearance is also given to some 

 minute tubes by a corresponding arrangement of the cytioplasm (figs. 

 36 & 40). 



No starch can be detected with the usual tests ; but in many filaments 

 there is evidently a bright sap-green tint, which is increased when light 

 is transmitted through the refractive cytioplasm. 



Throughout, the resemblance of the canals and their filaments to a 

 mycelium is very striking. 



Occasionally a long and wide canal, crammed with granular cytioplasm, 

 passes far into the substance of the coral and may be seen with those just 

 described. It can be traced outwards to the surface of the coral, whence 

 all the others come — some entering from without directly, and others 

 being branches of canals situated close to the outside or offshoots of what 

 appear to be cavities filled with oospores (Plate 5. figs. 2-5). 



