126 KEPOBT OX THE SPECIMENS OF THE GENUS MILLEPORA 



three times among all the coralla I have examined, so that it is probably very rare. I 

 am inclined to attribute it to the zooxanthellae which being present in large numbers 

 in these canals have, in drying, stained the corallum. In coralla that have been slightly 

 waterworn, I have occasionally seen this canal system marked out in grooves. 



The Spirit Specimens. 



Dr Willey sent me for examination a considerable number of specimens of different 

 forms of growth carefully preserved in spirit. 



I have decalcified large pieces and examined series of sections of specimens of 

 dichotomous and of complanate forms of growth and of five different fragments from 

 different localities. Unfortunately none of them show any signs of sexual organs. 



I have found the medusae of Millepora in three collections only, namely that of 

 Prof. Haddon from Torres Straits, of Mr Gardiner from Funafuti, and of Mr Duerden 

 from Jamaica. My experience is that when the medusae occur at all they occur in 

 great numbers. It is extremely probable therefore that further investigation of Dr 

 Willey 's specimens would not shew these organs. 



The examination of the sections however has led to some interesting results in 

 other directions. 



In the first place I may say that the anatomy of gastrozooids, dactylozooids and 

 coenosarc, and the size of the large and small nematocysts are the same exactly in 

 the dichotomous forms as in the complanate forms. No specific differences can be 

 drawn between the soft parts of these specimens, nor between the soft parts of these 

 specimens and those from other parts of the world which I have examined. Two 

 points of considerable interest in my sections of Dr Willey's material attracted my 

 attention, namely, the condition of the nematocysts and the presence of a curious 

 parasitic growth which has not hitherto been described. 



Nematocysts. In my earlier investigations on the structure of Millepora it 

 appeared to me that Moseley's account of the nematocysts of this genus was complete 

 and accurate, but the discovery of a spiral fibril running up the lumen of the thread 

 of the large nematocysts in some of the sections of Dr Willey's Millepores caused 

 me to undertake their investigation with great care. The result is that while 

 confirming the accuracy of Moseley's excellent observations in all essential details, I am 

 able to add one or two points which have not been recorded. 



As Agassiz originally pointed out, there are two kinds of nematocysts in Millepora 

 which are usually referred to as the large and small nematocysts respectively. 



The large nematocysts " never occur in the tentacles of the zooids, being confined 

 to the coenosarc, and being present in greatest abundance in zonal masses around the 

 bases of the zooids lying in the superficial layer of the ectoderm" (Moseley I.) 



Regarding the small nematocysts Moseley says they are of a kind "which 

 appears to be confined to Hydrozoa and not to occur at all in Anthozoa, viz. that 

 in which a bladder-like enlargement of the thread occurs at that part of it which 

 is immediately next the mouth of the cell, the bladder being armed near its summit 

 by three spines set in one whorl. The three spines in this form of nematocyst in 

 Millepora are remarkably long, and directed at right angles to the axis of the 

 thread, instead of recurved, as is usual. These nematocysts vary very much in size. 



