79 



Harvey's Fig. 2, PI. XLII (Nereis Bor.-Am., Part III) of AceL 

 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 away ; whether the 

 basal cell like that of A. mediterranea lives longer and is able to 

 develop a new plant I am unable to ascertain ; but it seems most 

 probable. 



This small Acetabiilaria seems to 

 me to be very closely related to Acet. 

 Farlowii and Acet. Suhrii. 



Acetabiilaria Farlowii, of which 

 species 1 have had specimens for com- 

 parison from the Bermudas collected 

 by M. A. Howe, seems however to be 

 distinguished commonly from A. Cali- 

 culus in having the apices of the rays 

 in the disc more or less broadly rounded, 

 and in that the Corona superior only 

 has two hair-scars and also that the 

 stalk has no or in any case only feeble 

 and few spindle-shaped swellings on 

 the uppermost part and finally that 

 the disc according to Howe is flat- 

 tened. But I may point out that 

 the specimens in one of my gatherings (Nr. 1617) from Long 

 Point in some regards bear a close resemblance to Acetahularia 

 Farlowii, especially by having the apices of the rays most often 

 broadly rounded and by seldom showing any indication of emar- 

 gination (Fig. 65). As the figure B shows, the Corona superior 

 almost had the same form as in my other specimens of A. Cali- 

 culus (cfr. Fig. 63 B) and had 2 — 3 hair-scars. The form of the disc 

 was basin-shaped. Yet this collection showed a peculiarity, 

 namely, that two of the specimens had two discs one over the 

 other thus resembhng Acet. crenulata, but even quite young plants 

 had the rays rounded or feebly undulated in the margin and not 

 at all apiculate as in A. crenulata, from which the plants were 

 very different. That however specimens are found, of which it 

 may be difficult to decide the species, is seen by M. Howe's remark 

 (1. c. 1905, p. 577) : »The zones occupied by the two species {A. Far- 



Fig. 65. Acetahularia Caliculus 

 Quoi et Gaimard. Forma. 



A, summits of rays. 



B, Corona superior. 



(4 about 15: 1,5 about <;0:1). 



