134 ZOOPHYTES. 



My chief anxiety has been to establish an absolute distinction among 

 the various species, if actually susceptible of being distinguished. Per- 

 haps they are not, and for all that has been said of the variety of the 

 number of parts, the tentacula may go no farther than the great variety of 

 colour among certain cpiadrupeds and birds constituting a genus, or even 

 a single species. 



Nevertheless, certain facts, about which there can be no controversy, 

 are derived from preceding observations, combined with the following 

 conclusions. 



Zoophytes, wherein the hydra is crowned by a head of a horse-shoe 

 or lunate form, with ciliated tentacula, are of three distinct genera, void 

 of any reciprocal kindred; the CristateUa, the Alcyonella, and the Pluma- 

 tella, to be thus described : 



I. CristateUa vagans [Mucedo], a fleshy basis, two inches long, and 

 above three lines broad, endowed with the slowest motion, sustaining a 

 border of 300 or 350 hydrse in a triple row, each provided with 100 ten- 

 tacula. 



1. Propagation ensues by lenticular formed ova, begirt by a circle of double 



recurved spines, generated in the fleshy basis, whence they are liberated 

 by its decay. 



2. An interval of 200 or 230 days is required for maturity of the embryo, 



after liberation of the ovum. 



3. The embryo, developed as a single white hydra, quits the ovum ; after 



which other hydne are developed from the same basis, their numbers 

 augmenting with time. 



4. In maturity the CristateUa is of a fine translucent green colour. 



II. Alcyonella. — A gelatinous, adhesive, immovable stratum, from 

 which the hydrse issue in extraordinary numbers. 



A. Alcyonella stagnorum. 



1. Invests leaves or stems of aquatic plants, in a grey stratum. 



2. The hydrse, numerous in proportion to the surface overspread, are pro- 



vided with from 42 to 44 ciliated tentacula. 



