t COLLECTED BY DR WILLEY. 129 



variations in this measurement, due I believe to the fact that some of them are, 

 when killed, slightly more oval than others, but on taking the average of a large 

 number of measurements the length is found to vary very slightly indeed from 

 02 mm. The small kind of nematocyst varies much more in size than the large 

 kind. The largest of them which I found in the tentacle of a gastrozooid (PI. XVI. 

 Fig. 6), was '02 mm. from the whorl of spines to the bas"e of the vesicle. The length 

 of the vesicle before explosion must have been about two-thirds of this measurement. 



Parasite. In two of the spirit specimens, one a foliate form from Sandal bay 

 and the other a plicate form, I noticed numerous white spots scattered over the 

 surface of the coral having the general appearance of a rash. On decalcifying a 

 portion of the specimen these spots were found to be quite irregular in form and 

 varying in size from minute dots to lumps half a millimetre or more in length. 

 It occurred to me that these bodies might be connected with the well-known parasitic 

 fungus Achlya penetrans, the mycelial threads of which are almost invariably found 

 in the deeper parts of the skeleton of Millepora. I have not yet detected these 

 threads in the living superficial layer of any Millepore I have examined, but 

 Moseley (I.) says, " They are not confined to the calcareous structure, but in Millepora 

 nodosa (from Tahiti) at least occur also in abundance in the soft superficial tissues." 



These bodies however are not apparently connected with the mycelial fibres, and 

 their microscopic structure does not suggest that they belong in any way to a fila- 

 mentous fungus. Each of the white bodies which can be seen on the surface by 

 macroscopic observation is seen in section to be composed of a number of irregular 

 lumps (PI. XVI. Fig. 7). These lumps are so irregular in form and size that it is 

 extremely probable they are due to shrinkage during preservation and of no morpho- 

 logical importance. Each lump consists of numerous minute lancet-shaped rods 

 ■004 mm. in length, arranged with their longer axes parallel. No trace of a membrane 

 or wall enclosing the bodies as a whole or the lumps into which they are broken 

 up can be found, and most of the bodies are completely isolated from their neighbours 

 by normal healthy millepore tissues in which none of the rods can be traced. 

 These rods readily stain in Haematoxylin, Borax-Carmine and Safranin, and when 

 teased out on a cover-slip, separate in rows rather than in strings, as shown in the 

 figure (PI. XVI. Fig. 8). 



The conclusion seems to be then that these bodies are clusters or zoogloeae of 

 parasitic bacteria which may provisionally be called Bacterium milleporae. I cannot 

 call to mind in the literature of the subject any previous note on the occurrence 

 of bacteria in corals, and I can find nothing similar to these bodies in any of the 

 preparations I have made of millepores and other hydrocorallines from other parts of 

 the world. (Cf. Duncan.) 



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