300' 



4. On Electra verticillata, with a notice of its dif- 

 ferent forms of growth. By E. W. H. Holdsworth, 

 F.L.S., F.Z.S., etc. 



(Radiata, PI. XIII.) 



The fact that but little attention has been given to a remarkable 

 variety of growth in Electra verticillata must be my apology for 

 bringing before this Society an animal that was first noticed more 

 than seventy years ago. Ellis described this species in 1786, under 

 the name of " Flustra verticillata,'''' or the " Basket-work Sea Matt," 

 from a specimen that he received from the Mediterranean ; and he was 

 followed by other naturalists, who retained the same title for it. In 

 1824 Lamouroux's translated work 'Corallina' was published in 

 England, from which it appears that, observing the branched poly- 

 pidoms and verticillate arrangement of the cells in this species, he 

 proposed a genus for its reception under the name of Electra ; and 

 in this he was supported by many subsequent writers, including 

 Risso, Cuvier, and Blainville, — the last-mentioned author, however, 

 stating that Electra could hardly be separated from Flnstra. 



Its true position appears to be close to Memhranipora, but distinct 

 from it on account of the regular transversely linear arrangement 

 of the cells under all its varieties of growth ; this will especially 

 distinguish it from Flustra, and in a less degree from Memhranipora, 

 where the quincuncial disposition of the cells is not so uniformly ob- 

 served, and their arrangement is more frequently irregular. I am 

 inclined to consider Lamouroux's view of the case correct, and shall 

 therefore retain the name that he proposed for the genus. 



Several naturalists have mentioned the occasional growth of 

 Electra in subcompressed linear fronds ; but the only published 

 figures of the species that I know — those of Ellis, Lamouroux, and 

 Blainville — are all taken from the cylindrical variety, which appears 

 to have been considered as typical. My own experience of Electra 

 rather points to this encrusting of slender branching sea-weeds as 

 exceptional, and the suberect ribbon-shaped fronds as being the most 

 common form. I have only observed the species in one locality 

 however — on the northern shore of Portugal, near Oporto, where 

 the free compressed variety is abundantly met with in a dried state 

 on the beach; fourteen specimens were obtained of this shape, and 

 only one was found of the cylindrical form usually described. The 

 eariv growth of the polypidom, however, is undoubtedly encrusting, 

 and' generally on Fucus ; but after the formation of a few cells on 

 the surface, the erect form is assumed, and dense clusters of narrow 

 ribbons spring up, with occasional branches budding from their edges, 

 each ribbon being composed of a double layer of connected opposite 

 cells, placed in transverse parallel rows of 10 or 12 in each. The 

 cells are compressed and cup-shaped, with the walls minutely punc- 

 tured, and have the margin surmounted by several irregularly 

 placed erect denticles, and a long curved vibraculum inserted a little 

 below the anterior edge. In the ribbon-shaped variety, these vi- 



