480 Analytical Notices of Books. 
alternation of expansion and contraction. In the more typical among 
these siphonizing animals the functions of nutrition and respiration are 
combined, their functions in general being much simplified, and per- 
formed. by the most simple organs, “ These organs,’’ le says, ‘ are 
tubular muscles, which are very sensitive, irritable and contractile, 
serving at once for nerves, vessels and intestines, They have hitherto 
been regarded by anatomists and zoologists as vessels: but the 
fluid contained within them flows backwards as well as forwards, and 
they effect in the Salpe and Medusa, a regular succession of contractions 
and expansions, closely resembling the systole and diastole of the brain, 
heart and lungs in the higher warm-blooded animals. The greater 
number of these animals have only one mouth, and all of them but a 
single stomach. Their digestive process consists merely in the absorption 
of their prey, and they require in consequence neither liver nor gall- 
bladder, neither proper intestine nor anus ; but their respiration appears 
to predominate over all their other functions, which are performed solely 
by means of the respiratory organs. By means of this action they 
progress in the sea; by its means they secrete their fluids; by its means 
they suck in their prey; by its means they assimilate the inhaled fluid ; 
by its means they expel their young; and even the embryos thus expelled 
are in the first instance developed by means of the commencing respiratory 
action in themselves. By the same means they excrete a luminous gas or 
nocturnal light, and by a redoubled exertion of this action they change 
their colour by day,”? It may here be added, that the authour appears to 
regard the aggregated Tunicata, such as Pyrosoma, Monophora of Bory de 
St. Vincent, Noctiluca and Telephorus, as the young fry of the simple 
species; but on this and many other points he is somewhat obscure. 
The observations of M. Chamisso, and more particularly those of MM. 
Audouinand Milne Edwards, shew that we have still much to learn before a 
definitive opinion can be formed with regard to the history of the Tunicata. 
There is little novelty in the authour’s principles of classification, as 
regards the subdivision of the family of Meduse ; his sections being 
almost wholly founded on those of Peron, and consequently too well 
known to require explanation. The species of Cassiopea described and 
