MR. HUXLEY ON THE ANATOMY OF SALPA AND PYROSOMA. 
589 
outer tunic, the distinction is of no value, systematically, as the character may vary 
greatly in the same or closely allied genera. 
Section IV. — History of our Knowledge of the Salpse. 
68. Forskahl, the Danish naturalist, founded the genus Saiga upon certain animals 
taken in the Mediterranean. No less than eleven species are described and figured 
by him (and with remarkable clearness and accuracy) in his ‘‘ Descriptiones Anima- 
lium,” a work which he unfortunately did not live to see published, but which made 
its appearance in the year 1775. 
The following is his definition of the genus: ‘‘Salpa corpore libero, gelatinoso, 
oblongo, utroque apice aperto ; intus vacuo; intestino obliquo variat: a) nucleo 
globoso, opaco, juxta anum b) nucleo nullo sed linea dorsali opaco. 
“Nomen mutuatum a 2aX7ra, pisce a Grmcis cognito et huic vermi additum ob simi- 
litudinem formse cum tubo canoro. Animal plerumque gregarium ; mira cohserens 
symmetria rnotum corporis per systolem et diastolem, siphonica arte perficiens.” 
Browne*, who appears to have been unacquainted with Forskahl’s work, gave 
the name of Thalia to some Salpce, which he describes and figures in the rudest 
manner. 
Bose seems to have been the first to suspect the identity of these two genera, 
a suspicion which was converted into a certainty by the researches of Cuvier, who 
not only disentangled the nomenclature of the genus from the confusion into which 
it had fallen, but gave the first accurate idea of the anatomy of the Salpce, and first 
announced their true zoological relations. 
69 . Much was added piecemeal to the foundation thus laid by Cuvier, by subse- 
quent authors. Meyen and Milne-Edwards described the nervous system, Kuhl 
and Von Hasselt, Eschscholtz and Milne-Edwards, announced the singular nature 
of the circulation. Cuvier and Chamisso hinted, and Meyen described, the pla- 
cental connexion of the solitary foetus with the parent ; EscHRiCHTand Sars declared 
the proximate nature and mode of origin of the Salpa chain. 
70 . Chamisso again founded the theory of the “ alternation of generations,” using 
that very phrase^f' to express the peculiarities accurately observed by him in the mode 
* Natural History of Jamaica, 1785. 
t Justice seems to have been hardly done to Chamisso as the first promulgator of the theory of the “alter- 
nation of generations.” He says at p. 10, “ Qua seposita (Salpdbicorni) alternationem generationum legem esse 
ut posuimus genericum, omnibus communem speciehus, observationihus innititur and at p. 3, “ Tabs specie! 
metamorphosis generationibus in Salpis duabus successivis perficitur, forma per generationes {neguaquarn in 
prole seu individuo) mutata. Verum enimvero qua lege proles Salparum, ut animal ab ovo, imago a larva, inter 
se differunt, parum elucet.” And in his interesting “ Reise um die Erde,” Chamisso shows still more clearly 
his distinct conception of the theory by the remarkable phrase, “ Es ist als gebare die Raupe den Schmetter- 
ling und der Schmetterling hinwiederum die Raupe.” “ It is as if the Caterpillar brought forth the Butterfly, 
and the Butterfly the Caterpillar.” 
Subsequent writers seem not to have done much more in reality than oring new cases under the law here so 
MDCCCLI. 4 G 
