1876.] parasitic within recent Madreporaria. 255 



The canals and included filaments in some instances increase in calibre 

 at certain spots, and even form globular expansions, but usually the same 

 diameter is retained; the enlarged portions relate to the reproductive 

 process. The cell-wall of the filament is in close contact with the scleren- 

 chjma of its canal. 



In a littoral species (CaryopJiyllia Smithi) the parasite is identical with 

 Saprolegnia ferax, Ktz. ; but there is a manifest distinction between it 

 and those of the other forms. The parasite of the littoral coral greatly 

 resembles those of the shells of MoUusca and of the scales of fish. 

 Although it is quite possible that all the parasites of the corals described 

 may be referred to one species, their type being altered by the peculiar 

 conditions surrounding them, still it is thought advisable to regard 

 them as members of two species. The classificatory position of the 

 parasites is in the midst of a group of forms which have complicated life- 

 cycles, such as the Achlyans (proper), the Saprolegnice, and Empusince 

 and Botritidae, and the filamentous false-root bearing genera Goclium and 

 Bryopsis — forms which are more or less the expressions of one organism 

 under different conditions and age. 



EXPLANATION OF THE PLATES. 

 Plate 5. 



Fig. 1. Balanophyllia verrucaria. A longitudinal section of the coral close to the end 

 of a septum, showing masses of the tubules of Achlya -penetrans close to their 

 entry. X 40 diameters. 



Fig. 2. CaryophyUia clavus, var. borealis. A large tubular excaration opening out at 

 the surface of the coral. X 350 diameters. 



Fig. 3. Another excavation. 



Fig. 4. A large tubular excavation cut across and exhibiting tubes of the parasite 



coming from it. X 350 diameters. The same coral as figs. 2 & 3. 

 Fig. 5. A transverse section of a tube found in the midst of the same coral ; it shows 



the porose condition of the tube-wall and some branches. The coral-structure 



around is not shown, X 350 diameters. 

 Fig. 6. The origin of a long parasitic tubule from a large entry-tube. X 350 diameters. 

 Fig. 7. The porose condition of the wall of the tubular cavity, and very minute tubules 



coming off from the perforation, and a long and larger tube are shown. 



X 350 diameters. 



Fig. 8. A series of dilatations in a large entry-tube. X 300 diameters. 

 Fig. 9. A large tube branching. X 300 diameters. 



Fig. 10. A partly normal and partly parasitically formed concavity at the edge of a 

 coral, with minute tubules and a larger tube coming from it and penetrating 

 the coral-structure. X 300 diameters. All these views from fig. 2 inclusive 

 are from the same coral. 



Plate 6. 



Fig. IL Flahellum laciniatum. Typical parasitic tube of Achlya penetrans filled with 



cell-wall and cytioplasm. 

 Figs. 12-15. Various shapes of typical tubes. 



Figs. 16, 18, 19. Tubes branching at right angles and terminating in a blunt or globular 

 head. 



t2 



