parasitic within recent Madreporaria. 



249 



the cytioplasm and partly to the existence in the canal-wall of minute 

 more or less perfect perforations. It is evident that the canals of these 

 large parasitic filaments may be correctly compared with the larger long 

 and short penetrations on the outside of the corals, which are the means 

 of entry of the bulk of the parasitic growths. 



VII. Method of Entry and Groiuth of the Parasite. 



It is evident from the examination of the sections of the outside of 

 corals that the parasite obtains entry below the living dermoid tissues of 

 the coral at spots ^^here there is usually a crowd of competitors for 

 attachment, shelter, and also for boring. Some minute cavities on the 

 outside, either the result of the operations of other organisms or the 

 product of the ornamentation of the coral, evidently and constantly con- 

 tain masses like large conidia or oospores or shapeless masses of granules. 

 The boundaries of these cavities often relate to the intermediate spaces 

 between columns of spicula peculiar to the coral sclerenchyma ; the 

 organic basis of the hard structures comes in abundance close to the 

 outside of the theca in such positions, and it is the partictdar food of the 

 mycelium about to enter. The tubule of the ingrowing parasite comes 

 from a conidium, oospore, or from a granular mass which probably is a 

 zoospore ; and the entry can only be by growth-force, and by the assimi- 

 lation and removal of the organic basis, together with the dissolution 

 of the carbonate of lime of the coral by the dev elopment of carbonic 

 acid from the end of the tubule. The existence of movement in the 

 cytioplasm and possibly in the cell-wall may be reasonably inferred ; and 

 this would tend to drive out fluid between the hard walls and the soft 

 internal tube. The solution appears, however, to be only active at the 

 growing end of the tubule ; and this growth is clearly often stopped by a 

 hard and solid mass of spicula, there being an insufficient quantity of the 

 organic film there for the nutrition and vis viva of the parasite. It is 

 evident that the entry must be made during the life of the corallite or 

 very shortly after death. 



There is one manner in which the parasite reaches the outside of the 

 coral and becomes fixed so as to penetrate, which is very remarkable and 

 also suggestive of the group of Thallophytes to which it belongs. 



Species of Bryopsis and Cladophora were living in the aquarium with 

 the Balanophyllice which were afterwards cut and, in some instances, 

 decalcified. These reticulate and dark green forms grew upon the lower 

 parts of the corals, \v here the bright orange animal matter was no longer 

 existing ; and, as the corals grew weak in their nutrition and the tentacles 

 rarely expanded, there was an evident struggle between the vigorous plants 

 and the dying Coelenterate. At last extremely fine filaments of Bryopsis 

 appeared on the septa, and, as the thin films of living tissue grew smaller, 

 they encroached more and more. 



I thought at first that the penetrating parasite was either a "rootlet" 



