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," he 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 vpithin them flows backwards as well as forwards, and 

 they efiect in the Salpce and Medmce, 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. 

 Audouin and 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 Bledusas ; his sections being 

 almost wholly founded on those of Peron, and consequently too well 

 known to require explanation. The species of Cassiopea described and 



