On the alternation of generations; or, the propagation and development of animals through alternate generations: a peculiar form of fostering the young in the lower classes of animals ... / By Joh. Japetus Sm. Steenstrup ... Translated from the German version of C.H. Lorenzen, by George Busk.

  • Steenstrup, J. Japetus Sm. (Johannes Japetus Sm.), 1813-1897.
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: On the alternation of generations; or, the propagation and development of animals through alternate generations: a peculiar form of fostering the young in the lower classes of animals ... / By Joh. Japetus Sm. Steenstrup ... Translated from the German version of C.H. Lorenzen, by George Busk. Source: Wellcome Collection.

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    preceding sections, and especially in the phenomena observed with regard to the propagation of Medusa aurita. This free swimming Medusa always produces a progeny which is polypiform, and destitute of the power of locomotion, but which on the other hand after attaching itself to various bodies at the bottom of the sea, brings forth a progeny consisting of free swimming Meduse, which never assume the polypoid form; and this alterna- tion is constant. The fact may be thus expressed: that each second generation is affixed and polypoid, or that the free swimming hemispherical Meduse always produce a polypoid ofispring, and that the polypoid Meduse are always the parents of the free swimming hemispherical ones, &c. I have consequently no hesitation in expressing my belief, that the alternate generation of the Salpe, from solitary and associated individuals, is to be explained in the same way as that of the Meduse, and that the first gene- ration of these animals serves as a series of foster-parents, whose object is, by their furthermg the development of the second generation, to conduce to the perfection of the species. I am, however, prepared to admit, that this kind of explanation does not enlarge our knowledge with regard to the propagation of the Salpe ; I only think, that the phenomena already known, will have a clearer hight thrown upon them from the analogy. Some doubt even must still remain, on the circumstance whether the solitary or the associated Sa/pe are the foster-parents. In my opinion however, it is the solitary form rather than the other which should be assumed to be that of the al * From a remark in Sar’s Memoir on the Meduse (Erichson’s Archiv, 1841, H. i, p. 29,) I perceive that that excellent observer has instituted re- searches on the development of the salpe, and promises to communicate them at another opportunity (which it is much to be desired should occur soon.) Although in the above place he does not state anything precise, with regard to the result of his inquiries, yet we may gather from what he says that Chamisso’s views and remarks are in the main correct. “ The salpe correspond in this with the medusa, that it is not their /arve which are de- veloped into the perfect animal, but the progeny of the /arve ; it is not the individual, but the generation which is metamorphosed.”