154 Prof. G. J. Allman on the Anatomy of Actzeon. 
General Observations. 
Such are the facts which, from a most careful examination of 
a great number of specimens, I believe myself justified m consi- 
dering as demonstrated. I took much pais in again and again 
verifying their correctness ; and as most of them have not as yet 
been recorded, while many are in direct variance with recently 
published statements, 1 lose no time in making them public. 
This I am the more desirous of doing, from the fact of the ana- 
tomy of our little mollusk having within the last year been as- 
sumed by an acute and indefatigable French zoologist as charac- 
teristic of a new order of Gasteropoda which he has thought fit 
to construct, but which appears to me to be constituted upon 
grounds totally msufficient, in some respects the result of im- 
perfect observation, and in others of conclusions which the ob- 
servations, supposing them to be correct, will in no degree 
warrant. 
In the ‘ Ann. des Sci. Nat.’ 2nde série, tom. xix., is a memoir 
by M. de Quatrefages on the anatomy of a small Nudibranchiate 
Gasteropod, which this naturalist conceives himself justified in 
separating, under the name of Holidina, from all previously cha- 
racterized genera of Nudibranchs. In this memow M. de Qua- 
trefages maintains, that in the anatomy of Kolidina there are pe- 
culiarities of such importance as to afford grounds for the esta- 
blishment of a new order among the Gasteropodous Mollusca. 
M. Milne Edwards had previously directed the attention of 
zoologists to a remarkable character of the stomach in the Eoli- 
dian Nudibranchs, demonstrating the existence in Calliopea of 
an extensive system of ramified canals connected with this organ. 
Upon this fact M. de Quatrefages seizes with avidity : he main- 
tains that the gastric ramifications perform the office of branchial 
vessels ; that they are therefore subservient to respiration as well 
as to digestion ; and finding them also in his Holidina, he con- 
nects them with other peculiarities which he asserts to have dis- 
covered in this mollusk, raises them to a rank of ordinal import- 
ance, gives them the name of phlebenteric system, and then sur- 
prises zoologists with the somewhat startling announcement of 
the existence of a new order among the Gasteropodous Mol- 
lusca. 
The doctrines which the examination of M. de Quatrefages’ 
Eolidina had thus led him to adopt, are carried out to their full 
extent in a subsequent memoir (Ann. des Sci. Nat. March 1844), 
in which, after the examination of Actwon and of five new genera 
of his own characterizing (Zephyrina, Acteonia, Amphorina, Pelta 
and Chalidis), he maintains the complete establishment of his 
new order, and enters into the details of its zoological affinities. 
