[ 567 ] 
XXIV. Observations upon the Anatomy and Physiology of Salpa and Pyrosoma. 
By Thomas Henry Huxley, Assistant- Surgeon R.N. 
{late of H.M.S. Rattlesnahe"). Communicated by Prof. Edward Forbes, F.R.S. 
Received February 26 , — Read March 27, 1851. 
1. The Salpce, those strange gelatinous animals, through masses of which the 
voyager in the great ocean sometimes sails day after day, have been the subject 
of great controversy since the time of the publication of the celebrated work of 
Chamisso, ‘De Animalibus quibusdam e classe Vermium Linnseana.’ 
In this work were set forth, for the first time, the singular phenomena presented 
by the reproductive processes of these animals, — ^phenomena so strange, and so utterly 
unlike anything then known to occur in the whole province of zoology, that Cha- 
Misso’s admirably clear and truthful account was received with almost as much dis- 
trust as if he had announced the existence of a veritable Peter Schlemihl. 
In later days an opposite fate has fallen upon the statements in question. They 
have been made the keystone of a revived* theory, and the phenomena presented by 
the Salpce have been cited as glaring instances” of a law governing the vast majo- 
rity of the lower invertebrata — the law of the “Alternation of Generations.” 
2. There appeared then to be two main points to be kept in view in examining the 
Salpce-. — 1st. Are the statements made by Chamisso correct? and 2ndly, if they be 
correct, how far is the “alternation theory” a just and sufficient generalization of the 
phenomena ? 
3. These questions, however, could not be entered upon without a thorough pre- 
liminary study of the structure of the Salpce, the opportunities for which are granted 
but to few. 
Such opportunities were afforded to the writer of the present paper at Cape York, 
in November 1849: for a time the sea was absolutely crowded with Salpce, in all 
states of growth, and of a size very convenient for examination. At subsequent 
periods the writer had occasion repeatedly to verify the results at which he had 
arrived, and to find strong analogical confirmation in the structure of Pyrosoma and 
other allied genera-f'. 
* Not new, see (70.). 
t Those who are acquainted with the nature of the service on which H.M.S. ‘Rattlesnake’ was engaged, 
will readily comprehend that the author’s investigations were almost necessarily original, and independent of 
anything going on in Europe. 
It is the more necessary to state this, as it will be seen, in the historical part of this paper, that M. Krohn,, 
4 D 2 
