402 TUBULARIA INDIVISA. 



however, was entirely misunderstood ; no one doubted as to its being a genuine sea plant, and 

 with this impression we find it described by the naturalists of that period under designations 

 indicative of a belief in its vegetality, such as that of " Adianthi aurei minimi facie planta 

 marina," under which it was recorded l)y Ray. 



In 1741 De Jussieu obtained it during a visit to the coast of Normandy, when along with the 

 actinozoal Alcyonium, and the polyzoal Flustra and Cellcpora, he made it the subject of iiis famous 

 memoir,^ in which, opposing himself to the general belief of the day, he not only supports the 

 views of Peysouel in favour of the animality of coral, but extends them to tlie plant-like Ilydroida 

 and Polyzoa. The figure of Tubularia indimsa which illustrates this memoir, though without 

 the manipulative skill of modern engravers, is admirable ; it is more exact than that subsequently 

 given by Ellis, and though the gonosome is not represented in it, it has remained up to the 

 present day unsurpassed in accuracy and expressiveness. 



In the former part of the present monograph the structure of Tubularia indivisa has been 

 fully described ; it has been shown how the coenosarc of the stems, instead of presenting the 

 usual axial cavity, is excavated into numerous peripheral channels, first pointed out by AVright, 

 with their walls all richly ciliated, and with the somatic fluid circulating through them in 

 advancing and returning currents, and how the endodermal lining of the Jiydranth cavity is 

 thrown into pendulous lobes and marked by deep intersecting sulci. It has been shown that the 

 longitudinal fibrillse, conspicuous in the tentacles, are formed by series of very much elongated, 

 fusiform, nucleated cells, presentuig thus the essential structure of the non-striated muscle of 

 higher animals. The structure of the gonophores has also been fully detailed, with their four 

 conspicuous, radiating canals, opening into a small circular canal which surrounds an orifice in 

 the distal end of the gonophore, through which the contents of this body escape at the period of 

 maturity. It has been further shown that the ova have their origin in differentiated masses of a 

 granular plasma, which is developed as usual between the endoderm and ectoderm of the spadix, 

 and which in its early condition consists of nucleated cells; and that these ova are developed 

 into actimdcE, though no evident germinal vesicle nor any true process of segmentation has as yet 

 been detected in them. And further, the remarkable phenomenon first noticed by Dalyell of the 

 successive shedding and renovation of the hydranths has been described, and it has been shown 

 that the new hydranth is produced by a metamorphosis of the distal end of the decapitated stem 

 rather than by a true budding.^ 



Few more beautiful objects present themselves to the student of marine life than a well- 

 developed specimen of Tubularia indivisa. From a complicated and intertwining mass of stems 

 where the hydroid roots itself to some submarine rock or the surface of some old shell, it gradu- 

 ally becomes disentangled, and soon displays a group of flexile cylindrical stems, rising without a 

 branch to the height of many inches, and each crowned by a scarlet or crimson hydranth, with its 

 double coronal of tentacles. The longer tentacles now spread abroad like the petals of an ex- 

 panded flower, now closed in over the summit, like the same flower in its bud, and now again 

 thrown back in gentle curves round the summit of the supporting stalk, while the long pensile 



^ Bernard de Jussieu, in ' Mem. Acad. Roy. dcs Sci.,' 1742. 



■ The details of the morphological and physiological facts here referred to will be found in 

 pages 69, 121, 131, 205, &c., and pi. xxiii. 



