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The segments of Corona superior (Fig. 6 B) have a somewhat 

 irregular form, oblong cordate, often somewhat emarginated on 

 the side turned outward and bear 2—3 hair-scars. In some spe- 

 cimens we generally find two scars, seldom three, in others three 

 and only seldom two. They may be found one behind the other 

 or quite irregularly. The shape of the Corona superior therefore agrees 

 well with the figure of Solms and the same may be said of that 

 of the Corona inferior (Fig. 6 C) ; the segments are here almost rectan- 

 gular, but somewhat laced in the middle. The breadth of the disc 

 is about 3 — 5 mm. 



The gametangia are spherical and occur in a number of about 

 80 in each ray. They are about 160 p. broad. A very large 

 number of gametes are developed in them. Contrary to what is 

 the case in Acetabularia mediterranea where the gametangia get 

 free and only after a resting period, often lasting several months, 

 •develop the gametes, these here come to existence while the game- 

 tangia are still enclosed in the rays. The gametangia are opened 

 by means of a similar cover as in A. mediterranea. At the same 

 time as the gametangia are opened, large holes are formed in each 

 corner of the rays most probably by decomposition of the walls, 

 through which holes the gametes can escape. It seems that these 

 holes arise simultaneously in all the gametangia of the disc, at all 

 events it has been the case in all the discs I have seen in this 

 stage of development. The gametes are ovate and have most 

 probably two cilia which I have not seen, though the gametes were to 

 be found here and there in the emptied gametangia or in the rays; 

 I have seen them lying in couples or more or less joined together, 

 also some larger roundish bodies were found most likely zygotes 

 and longer cylindrical cells: young plants. 



Yet I may add that the plant does not seem to have any 

 fixed growing or resting period; at any rate plants collected in the 

 months of January and February were found in all different stages 

 of development. I have found quite young plants without disc 

 but with two or three whorls of hairs in accordance with Harvey's 

 figure 2 PI. XLII (Nereis Bor.-Am.) of Acet. crenulata; plants were 

 found on which the disc was as yet quite small and had a whorl 

 of hairs in the corona superior; individuals were found on which 

 this whorl of hairs had fallen off but where the formation of the 

 gametangia had not yet begun and so on, until also individuals 

 with emptied gametangia were found. Now the disc and stalk die 



