Professor Agassiz's Zoological Researches. 319 



The Hydroides have a general cavity of the body, below 

 the stomach, into which the latter opens, as in the Actinia. 

 The walls of this cavity are provided with longitudinal and 

 circular muscular fibres, and the ovaries, suspended below 

 the tentacula, nevertheless open into this general cavity, 

 still as in Actinia. The clusters of the ovaria are simply 

 reversed. The stomach itself likewise projects between the 

 tentacula ; but it opens into the general cavity of the body, 

 as in the Actinia. The tentacula alone are really different, 

 being filled instead of tubular (which renders their motions 

 much less active), and the base of the body is prolonged in 

 a stalk fixed to the ground. The difference between the 

 Alcyons and the Actinias almost completely disappears, in 

 proportion as we learn to recognise the analogy of their 

 parts. Examine the stomach and ovaries, and you have a 

 true Actinia. 



I shall confine myself to saying that I am fully of Mr 

 Edward's opinion, who brings the Bryozoaria near the Mol- 

 luscs. I shall even add, that I am able, in some measure, to 

 demonstrate in detail the analogy of these animals with the 

 Acephali, from the disposition of their respii-atory and fcecal 

 orifices, to the arrangement of the interior organs. 



An insulated fact of great interest observed in a Lucer- 

 naria is, that this polypus has ocelli, eight in number, iden- 

 tical in their appearance with ihe eyes of the Echinodermcs 

 and Medus£E, and placed in the notches among the tentacular 

 fasciculae. 



Topography of the Pennine Alps, and Frimitive Site of the 

 Principal Species of Rocks found in an erratic state In the 

 Basin of the Rhone. By M. A. GUYOT. Communicated 

 by the Author. 



M. Guyot finished his explanation of the results of a jour- 

 ney he made last summer into tlie most elevated and least 

 known ])ortion of the Pennine A1i)h, the principal object of 



