246 Prof. P. M. Duncan on Thallophijtes 



Longitudinal sections made parallel with the septal ends often exhibit 

 these glomeruli to perfection ; and under a low power they may be seen as 

 bright refractive tube-masses entering the coral at stated intervals. This 

 appearance is also presented in old corals in transverse sections (fig. 29). 



Observations on Decalcified Sjpecimens of the Outer Paints. — After sub- 

 mitting sections or pieces of corals known to present the appearances just 

 enumerated and described to dilute hydrochloric acid until the hard parts 

 are destroyed and the organic basis-structure remains free, they should be 

 washed in distilled water ; and portions of the remaining matter may be 

 put up in thin cells with glycerine shghtly diluted. 



The organic tissue is usually preserved in films, but occasionally, and 

 especially in the semiperforate Balanophyllict', masses of it may be obtained 

 conforming to the widely reticulate structure of the exterior of the coral. 

 It is transparent, almost homogeneous, and only granular here and there ; 

 but the paths of many fine parasitic filaments may be traced in it. "Usually 

 the occurrence of larger canals determines the raggeduess a,nd breaking- 

 up of the organic film as a whole, as they have drilled through and along 

 it in all directions. 



Surrounding this tissue, and usually inseparable from it, are the vege- 

 table parasites, now freed from their calcareous covering. 



Reproductive Elements. — Oospores, zoospores (non-ciHated), separate or 

 in masses, aud the latter often within filaments, large confervoid-looking 

 filaments, large unicellular tubules crowded with dark cytioplasm, and 

 filaments of different lengths and diameters and with numerous or few 

 branches (all bearing a definite relation in point of size to the canals 

 whence they came) are readily seen and distinguished. 



The extremely fine canals, inch, do not usually yield any fila- 



ments after decalcifying has been even very carefully done ; but I have 

 been able to draw a few, which are all the more interestiug because they 

 are evidently extremely delicate utricles arising from the fusiform or 

 roundish zoospores which in this parasite, as in Saprolegnice, germinate 

 before expulsion and before having reached their true zoospore or mobile 

 condition. In Plate 7. fig. 55, zoospores are seen with filaments, and 

 in fig. 61 separate spores are delineated. 



It is evident, after the examination of these filaments and their asso- 

 ciated zoospores, that the cause of the furry appearance of some larger 

 canals (Plate 6. figs. 21, 22, 23) is due to the development of correspond- 

 ing growths from germinating cells within and their penetration of the 

 hard parts after having perforated the parent cell-wall and the dense struc- 

 ture surrounding. 



Earely a minute tube may be seen passing off at right angles from one 

 of the largest kind ; they are usuaEy short, and do not appear to come 

 from within, but to be offshoots of the parent ceU-wall. 



Oospores are to be found closely adherent to the organic basis-structure 

 and amidst the branching thread-like tubes which are inseparably attached 



