ANATOMY OF THE HYDROSTATIC ACALEPH.E lOI 



^'housed"), for the latter division, and that of A ncedoa for the former. 

 Now a mutual I'epresentation runs through these two groups. For 

 instance, the Actinidse represent the Hydra and its allies ; the Zoan- 

 thidae represent the Corynidae ; the Physophoridae seem to represent 

 the Pennatulidae ; and the Medusidse, the Beroids. Furthermore, 

 each group returns into itself; the free floating Actiniae nearly 

 approximate Beroe, and Lucernaria is but a fixed Medusa. 



Should these considerations eventually prove to be well-founded, 

 the author considers that it will be necessary to break -up the class 

 Radiata of Cuvier into four groups, severally capable of being defined 

 by positive characters. Supposing the Nematophora to form a sort of 

 central group, we have on the one hand the Asciclians and the 

 Bryozoa, leading to the Mollusca; on the other the Echinoderms and 

 Entozoa (in the widest sense), leading to the Annulosa ; whilst the 

 Polygastria, Sponges, and Gregarinidae (if indeed they are not rather 

 to be considered only as the lowest forms of the other three groups) 

 conduct us towards the lowest plants. These relations may be thus 

 represented : — 



MOLLUSCA. ANNULOSA. 



Ascidians. / Bryozoa. Echinodermata. Entozoa. > 



RADIATA. 



NEMATOPHORA. 

 Anoecioa- CEcioa. 



PROTOZOA. 

 Polygastria. SjDongiadfe. Gregarinidfe. 



PROTOPHYTA 



