356 REVIEWS. 



give in the space at our disposal would prove generally acceptable, and 

 might lead some to the study of an original, instructive, and beautiful 

 book. 



The Spongiadse should be regarded as a class of the subkingdom Pro- 

 tozoa, occupying an intermediate position between the Ciliata, or In- 

 fusoria, as that term is now limited, and the Rhizopoda, which may 

 justly be regarded as exhibiting the lowest type of animal life. The 

 Spongiad^e have been by many, and are still by a few, referred to the 

 vegetable kingdom, but the characteristics of animal life are too plainly 

 manifested by them for it to be easy, in consideration of what is now 

 known of their structure, to resist the evidence which places them as 

 not even the lowest of animals. If the true sponges are alone kept in 

 view. Dr. Grant's name, Porifera, may seem most appropriate, but we 

 cannot resist the inclination to place the Thallassicollidse certainly, and 

 the Gregarinidse probably, in the same class, in which, (unlike the 

 Rhizopoda,) whether single or associated in masses, each animalcule is 

 enclosed by a special membrane or skin, but there is no oral or other 

 definite aperture, the least possible differentiation of internal parts, 

 and when there are cilia they are used to create currents through open- 

 ings in a complex mass of animalcules, not for the purpose of indi- 

 vidual locomotion. With this view of the class the name Porifera 

 loses its applicability and another seems to be required, for still stronger 

 objections lie against DeBlainville's name, Amorphozoa. We adopt Pro- 

 fessor Reay Greene's definition of the highest class of Protozoa, which 

 we prefer to call Ciliata rather than Infusoria, the latter term having 

 been used very vaguely, and conveying no distinctive meaning. Ciliata 

 are animals belonging to the suhkingdom Protozoa, provided with a 

 mouth and rudimentary digestive apparatus ; their bodies usually con- 

 sisting of three distinct layers, the outer of which is, in most cases, 

 furnished with a variable number of Cilia. Rhizopoda may, we think, 

 be defined : Animals belonging to the suhJdngdom Protozoa, often 

 contained in a hard enclosure of variable substance, but never having a 

 differentiated skin or cilia; usually, perhaps constantly, with a nucleus, 

 but with no other permanent- distinction of parts ; taking their food 

 by protrusion of the sarcode ivhich forms their substance so as to 

 enclose the prey, and performing any movements of which they 

 are capable by the same means, these protrusions being called pseudo- 

 podia. Betv\een these two classes comes in that of which we are now 

 treating, and which we are disposed to define as follows : Anitnals be- 



