Our learned author here divides the animal kingdom into what may be denominated five sub-kingdoms or provinces, in three of which (with the exception of the _Crustacea_ and _Arachnida_ belonging to his _Annulosa_) no circulation of blood is visible, but which obtains in the rest. These he names-- 1. ACRITA, consisting of the _Infusory Animals_, the _Polypi_, the _Corallines_, the _Tæniæ_, and the least organized of the _Intestinal Worms_. 2. RADIATA, including the _Jelly-fish_, _Star-fish_, _Echini_, and some others. 3. ANNULOSA, consisting of _Insecta_, _Arachnida_, and _Crustacea_. 4. VERTEBRATA, consisting of _Beasts_, _Birds_, _Reptiles_, _Amphibia_, and _Fishes_. 5. MOLLUSCA, including the numerous tribes of _shell-fish_, _land-shells_, _slugs_, &c., which, from their mucous or gelatinous substance, from their nervous system and the imperfection of their senses, return again to the _Acrita_, though connected with the _Vertebrata_ by having a heart and circulation. His next set of circles shows the sub-division of these five sub-kingdoms into classes--Thus: [Illustration] In this scheme the _osculant_ classes are those placed between the circles. In the _Mollusca_ circle two classes are still wanting to complete the quinary arrangement of that sub-kingdom. I am not sufficiently conversant with the details of the animal kingdom at large to hazard any decided opinion upon Mr. MacLeay's whole system, or to ascertain whether all these classes are sufficiently distinct[21]. My sentiments with regard to those of the _Annulosa_ I shall state to you hereafter.