1898.] SPECIES OP MILTiEPOKA. 255 



the small nematocysts render them difficult to measure, but the 

 large nematocysts can be scraped off the surface of any pre- 

 served specimen in considerable numbers. The average size of 

 these nematocysts when ripe in specimens from Celebes, Bermuda, 

 Bahamas, I'unafati, Eotuma, the Eed Sea, Jamaica, and New 

 Britain is exactly the same — 0-02 mm. x 0-025 mm. The number 

 of the nematocysts varies considerably, but as this must be 

 influenced by the manner in which the specimens were killed, and 

 by external" conditions affecting them before they were killed, no 

 differences of specific value can be framed from this feature. 



The general anatomy of all these forms is in other respects, as 

 well as those mentioned, so much alike that I know of no means 

 of distinguishing one series of sections of well-preserved material 

 from another. There are no features of the soft parts which indicate 

 in the least the general character of the form and structure of the 

 skeleton they secreted. 



By far the most interesting and in many respects the most 

 important structures of these corals are the generative organs, and 

 to them we should naturally turn for characters which might 

 assist in distinguishing species. Unfortunately, however, our 

 knowledge of these structures is vei-y meagre and does not at 

 present help us very much. 



In the specimen presented to me by Prof. Haddon from Torres 

 Strait, I discovered that the male sexual cells migrate into dactylo- 

 zooids which become converted into medusae. These medusae, 

 when ready to become free, are situated in ampullae, which are 

 approximately 0'4 mm. in their greatest diameter: that is, in holes 

 in the skeleton larger than the largest gastropores. In another 

 specimen of a different mode of growth presented to me by 

 Mr. Gardiner from Funafuti I found numbers of these medusae in 

 ampullae of exactly the same size. The meduste of these two forms 

 are quite indistinguishable one from another. It seems probable, 

 then, that the Millepores from Zamboanga (Quelch), Jamaica, and 

 several others from unknown localities in which ampullae of this 

 character have been described bore in the living state medusae. 

 No gaps similar to these can be seen in any of the preserved 

 specimens which have been examined except those which contain 

 or have contained medusae. The fact that the largest ampullae of 

 all specimens are of approximately the same size, coupled with the 

 fact that the medusae of such different forms as those given me by 

 Mr. Gardiner and Prof. Haddon are exactly similar, suggests that 

 the medusae of all Millepores are similar. At any rate, there is no 

 evidence at present that there is any difference between the medusae 

 of the different forms. 



It is a very extraordinary fact that the ampullae are so rarely 

 found. I have had the opportunity of examining carefully a very 

 large collection of Millepores collected in the West Indies, and 

 deposited in the Liverpool Museum. I failed to find a single 

 ampulla in any one of them, but a small skeleton sent to me by 

 Mr. Duerden from Jamaica exhibited an immense number of them. 



