258 THE POPULAR SCIENCE MONTHLY. 



to his -well-matured principles, Chamisso contested in a special 

 memoir.* 



As a reward for his earnest exertions, and also as a warning 

 against too narrowly limiting the circle of possibilities in organic 

 nature, Chamisso himself was destined to make one of the most 

 remarkable discoveries in the region of metamorphism. This was 

 in the case of the Salpce,, those soft, transparent organisms which, 

 clinging to one another, swim over the sea in chains of from 

 twenty to forty members. Besides the chains there are individual 

 salpse, but of two kinds, one of which bear traces in their organs 

 of adherence of having been members of a chain, while the others 

 do not. During a calm, on the voyage from Plymouth to Ten- 

 eriffe, Chamisso made the surprising observation that the indi- 

 vidual salpse which have never belonged to a chain bear a progeny 

 resembling the chain salpse ; while he found in the members of a 

 chain young of forms agreeing with those of the single salpa. 

 The salpse of the chain, which produce single salpse, are hermaph- 

 rodite; the single salpse are asexual, and the chains are devel- 

 oped in them without fertilization, by inner budding. They 

 thus alternate every two generations, one of which is sexual, and 

 the other asexual and propagating itself by budding ; and they 

 are distinguished by other marks. To use Chamisso's figure, a 

 salpa does not resemble its mother or its daughter, but its grand- 

 mother, its sisters, and its aunts. Chamisso called this kind of 

 propagation that by alternating generations. So new and unpre- 

 cedented was this discovery that, although Chamisso related it 

 after his return in 1819, in a special Latin publication,! it either 

 passed unheeded, or was stamped upon. But there came to Copen- 

 hagen, in 1842, a defender and champion of Chamisso's fame in J. 

 Steenstrup, who discovered that the process of propagation by 

 alternating generations such as Chamisso described was common 

 to a series of organisms, including the Medusae, and Strobilce, the 

 Cercarice. and Distomce,, and the aphides or plant-lice, to which 

 many others have since been added ; so that the whole matter 

 was cleared up in a trice. Johannes Miiller's famous discoveries 

 concerning the development of the echinoderms furnish a tran- 

 sition between the phenomena of alternation and those of meta- 

 morphosis as illustrated in the frogs and butterflies. The honor 

 of having led the way to these discoveries belongs, as Steenstrup 

 has expressly declared, to the accurate and ingenious investigator 

 Chamisso. f 



* Ein Zweifel und Zwci Algen (One Doubt and Two Sea-weeds), 1829. 



f De animalibua quibusdam c classe vermium Linnaeana in circumnavigatione terra 

 . . . obscrvatis, etc. (On Certain Animals of the Linnsean Class of Worms observed in the 

 Circumnavigation of the Earth.) Fasc. 1, De Salpa. Berlin, 1S19. 



\ Steenstrup on Alternating Generations. Copenhagen, 18-12. 



