TA THE LIMITS OF THE CLASS OF FISHES. 
froy St.-Hilaire * had, in 1852, separated from the class of fishes 
as the type of a new class (Myelozoa) the genus Branchiostoma or 
Amphioxus (a species which was originally described by Pallas as a 
member of the molluscan genus Limax), rediscovered and first 
referred to the class of fishes by Costa in 1834. Bonaparte, at the 
same time, proposed to withdraw from the invertebrates the genus 
Sagitta (Quoy and Gaimard) and elevate it to the rank of a 
class (Aphanozoa) of the ‘vertebrates. 
In the elevation of Sagitta to the rank of a class Bonaparte 
has anticipated Professors Carus and Huxley (who also elevated 
the same form to class rank, retaining the name Chetognatha, 
originally conferred upon it as the type of an order by Leuckart). 
But his views respecting its pertinence to the branch of verte- 
brates are untenable, for there can now be no doubt that it is 
at least most nearly related to the class of annelides. 
In 1857, the question of the primary classification of fishes was 
again reviewed by Prof. Agassiz. That eminent zoologist ‘was 
satisfied that the differences which exist between the Selachians 
(the skates, sharks, and Chimerz) are of the same kind as those 
which distinguish the amphibians from the reptiles proper and 
justify, therefore, their separation, as-a class, from the fishes proper. 
I consider also (he adds) the Cyclostomes as a distinct class 
for similar reasons; but I am still doubtful whether the Ganoids 
should be separated also from the ordinary fishes?’ He finally 
however admitted four classes, viz :— 
‘Ist class; Myzontes with two orders, Myxinoids and Cyclos- 
tomes. 
(Suite et fin.) <<Comptes rendus hebdomadaires des séances de l'Académie des Sci- 
ences, (ler Dec. 1856) XLIII, 1017-1027. 
* Ihave been unable to find any memoir ork by Geoffroy St.- 
aire embod tte the view referred to, and kapeat it may have bis a verbal commu- 
nica ation, and n punpa published. 
tQue le Sasina, Q Quoy et Gaimard, cet animal singulier si commun dans les mers du 
Nord, découvert par nos intrépide es voyageurs, et ballotté par les savants entre les 
Mollusques, us Vers et jusqu’ aux Acaléphes! posséde dans la première période de 5a 
rétrograde dans le sens de Rathke. C’est à M sner, jeune professeur à , 
qu’on doit cette belle découverte. Cet animal, qui dans létat actuel de la scien 
que comme un Poisson, ainsi dire, d é, mériterait de 
former une classe à part, bien plus oore s PAmphyoxus ou ahprmpones "a 
asse 2 des caked ipepe j, depuis 
' En afat 1 A £ < zt Tat tiel ertébrés) soos 
: et disparaissant surat dans Paduka peaa un caracire tellement impor- 
_ tant, qu'il n e peut désigner un groupe @an | rang moins élevé q elui de aha il 
it Se con ne Pee eae ko PES os Aphanozoa. 
