178 ZOOPHYTES. 



which the twigs issue in alternate arrangement. The upper surface of 

 each twig is clothed with two rows, somewhat apart on the surface, of al- 

 ternate minute low denticles or cells, inhabited by very minute pure white 

 hydrse, having 15 or 16 muricate tentacula. The extremity of a branch, 

 with its tenants, is represented as seen by the microscope. — PL XXXIV. 

 fig. 1. 



Both the organic and inorganic parts, I mean the skeleton, together 

 with the hydra and its cell, are regenerated in the Sertularia falcata. The 

 whole twigs of a specimen five inches high, bearing 24 branches, had suf- 

 fered mutilation. But above 100 parts, with several hundred cells and 

 hydrse, all pure white, were regenerated in March and April. A great 

 contrast distinguished these reproductions from the older portions. 



During spring, especially in March and April, and in the beginning of 

 May, numerous white or yellow vesicles load the Sertularia, each colour 

 belonging to its respective specimen ; the two never being interspersed on 

 the same specimen. The vesicle itself is perfectly transparent. Thus its 

 colour is derived from the contents ; but the yellow has always appeared 

 larger than the white. Numbers of the yellow crowded together on a 

 branch, perhaps 30, 40, or even 50 at a time, resemble so many minute 

 lemons both in shape and colour. — Plate XXXIV. fig. 2. There seems no 

 difference in the profusion of the white and the yellow, and the cells in the 

 neighbourhood of either are occupied by living hydrae. Both are like an 

 ovoidal flask, with a short tubular neck and a circular orifice, some having 

 a margin or reflected lip, fig. 3. 



The side of the vesicle is of such transparence as to expose what is 

 within, and there from one to seven corpuscula may be enumerated. — 

 Figs. 4, 5, 6. 



Having selected portions of the Sertularia, with a number of yellow 

 vesicles for a regular series of observations, I remarked some slight move- 

 ment among the contents. The general configuration, the relative posi- 

 tion, and the aspect of the included subjects, were changing ; and in fif- 

 teen miiautes the separation of one corpusculum, which rose above the 

 other, proved its animation. It ascended slowly towards the orifice, and 

 issued forth as leisurely ; but when reaching the surface of the glass below, 

 its course was sufficiently accelerated. This animal was of vivid yellow 



