ACALEPH^. 185 



Sars, in 1833, discovered a gelatinous Polype differing from the 

 Hydra gelatinosa hy its thicker body, slightly marked by transverse 

 rings ; believing it to be a new genus of Polype, he described 

 it under the name of Scyphistoma (Jig. 89.). In the same year 

 Sars also described a gelatinous polypoid animal, differing from the 

 above in the deeper annulation of its thicker body, the rings of which 

 developed bifid processes {Jig. 90.) ; and he called this very sinijular 

 creature Strobila, from its resemblance to an artichoke. He finally 

 saw the rings or segments separate from one another {Jig. 91.) and 

 swim off as little medusas {Jig. 92.).* 



At the meeting of the British Association, at Edinburgh, in 1834, 

 Sir J. G. Dalyell communicated his observations on a marine Hydra, 

 which he had called Hydra tuba, or the trumpet-polypus ; he 

 described it as about five lines long, and with about thirty tentacula, 

 stated that it was very predacious, would gorge young actiniae, and 

 discharge the rejectamenta again by the mouth. It was very sensitive 

 to light, contracting and retreating from it. It was not very locomo- 

 tive, and propagated by complete gemmation, the young not removing 

 themselves very far from the parent. 



In his later workj, published in 1847, Sir J. Dalyell remarks, 

 " Hence it is natural to assume that a germ, or deposition of elemen- 

 tary matter, subsists somewhere in the flesh," and that " generated 

 within as a compact substance, its Avay is made, by a regular process, 

 to the exterior, where it becomes visible as a rising prominence." 

 And at page 89. he asks, " Whether the budding results from a germ 

 come of an earlier principle," which shows how nearly the ingenious 

 author had arrived, by independent thought, at the true condition of 

 parthenogenesis. J 



Upon the whole, Dalyell has given us the best history of this 

 polype stage of the Medusa, of its longevity, of its powers of propaga- 

 tion by gemmation, and also its powers of repairing injury. To give 

 an idea of the reproducing force in the Hydra tuba : on April 23rd 

 an adult was detached from its site and insulated; in four days a spur 

 or bud had issued from one side of the base, and a large protuberance 

 with a row of papillae, an originating embryo, was rising from the other. 

 On the 2nd of May these papillae had elongated into perfect tentacuJa, 

 like those of the adults. Another protuberance on the opposite side 

 of the parent was now visible, which gradually matured into a young 

 hydra, and began to feed on the 17th. On the 30th of May separa- 

 tion had taken place ; four individuals were to be observed, and one 



* CLVI. t CIX. vol. 1. p. 82. 



X First pointed out in LXXXIV. (1843), pp. 234. 36G. 



