SERTULABJA. 



259 



Genus SERTULARIA, Linnaus (in part) . 



DYNAMENA, Lamouroux (in part). 

 AMPHISBETIA, Agassiz (for S. operculata). 



GENERIC CHARACTER. Zoophyte plant-like; stems more 

 or less branching, jointed, rooted by a creeping stolon; hy- 

 drothecae biserial, opposite, or alternate, without external 

 operculum ; gonothecce. scattered, with a simple orifice, and 

 without an internal marsupium. 



Fig. 32. 



THE genus Dynamena was constituted by Lamouroux 

 for the Sertulari<B which have the calycles opposite and 

 in distinct pairs (Woodcut, fig. 32) . Of 

 this group one section is now referred 

 to Diphasia; and I can see no valid 

 reason for separating the remaining 

 species from those with alternate and 

 subalternate calycles. The character 

 relied upon by Lamouroux as diagnostic 

 is a very shadowy one. In such a spe- 

 cies as Sertularia filicula, the hydro- 

 thecse are commonly opposite, but they 

 are also in many cases subalternate. 

 On some shoots they occur regularly in 

 pairs, and usually with a joint between 

 each pair, as in S. pumila; on others 

 they alternate slightly, and as many as six are borne on 

 an internode. If the genus Dynamena were adopted, S. 

 filicula must be referred to it*, and would thus be separated 

 from S. abietina, to which it is clearly most closely related. 

 It is impossible to draw a boundary line satisfactorily ; and 



* So Kirchenpauer places it, in a recent paper (1864), in which he has 

 argued for the retention of Lamouroux's genus. 



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