444 POSITION OF THE POLYZOA. 



indeed which is valuable even at the present day, owing to the invariable clearness and 

 occasional brilliancy of the descriptions, and the number and accuracy of the engrav- 

 ings. 



Ellis called all these creatures by the name of Corallines, a title now given to one of 

 the true vegetables, but discovered many anatomical and physiological details, and set 

 their animal nature beyond a doubt. All his researches were conducted with the aid of 

 instruments which in our day would be thought almost useless, the microscope em- 

 ployed being only a simple lens mounted on a stand, and devoid of the complicated ap- 

 paratus for magnifying and illuminating that now afford such aid to the observer. 



After the animal nature of the Polyzoa had been fairly established, they were con- 

 founded with many other marine and aquatic inhabitants, such as the corals and the 

 various zoophytes, in consequence of the superficial resemblance between their external 

 forms. Lately, however, their true place in the animal kingdom has been discovered, 

 and their affinity with the lower molluscs clearly proved, the tunicates forming the con- 

 necting link between the molluscs proper and the molluscoids, as these animals are 

 sometimes called. 



Having glanced at the general history of these curious and really beautiful animals, 

 we will proceed to examine the form and characteristics of the individual species. 



Should the reader obtain from the sea or fresh water a being which is evidently 

 either a zoophyte or one of the Polyzoa, he may set his doubts at rest by examining the 

 tentacles, and if he finds that they are furnished with cilia, or minute filaments, he may 

 assure himself that they belong to the group of animals on which we are now engaged. 



The forms assumed by the general mass of the various species of Polyzoa are ex- 

 tremely different, some resembling twigs or mosses ; others looking like lumps of spongy 

 substance adhering to sticks, stones, or leaves, or even lying freely in the water; others 

 being flat and ramified, like broad-leaved seaweeds ; others spreading film-like over leaves, 

 stones, shells, or similar objects ; while a few are able to crawl at liberty, the entire 

 organism being animated by some wonderful instinct, which urges all the myriad in- 

 dividuals of which it is composed to employ their force in the same direction. 



The number of these creatures is so vast that it is impossible to give more than a 

 brief description of them ; but in the following pages it will be found that a careful 

 ! selection has been made of the typical forms, and that sufficient details of their struct- 

 ure v ^e given to enable the reader to form a general idea of the subject, and in most 

 cas' .efer any specimens which he may find to their genera or families. Those who 

 de .urther information on the subject will find it in Busk's elaborate catalogue of the 

 M ,ie Polyzoa, in the British Museum, and the large work by Allman on the Fresh- 

 w.xer Polyzoa, published by the Ray Society. 



Putting aside the classification of the polyzoa until the termination of the work, we 

 will proceed at once to the description of the many species on our illustration, delineated 

 by the accurate pencil of Mr. Tuffen West. 



The first family of the polyzoa (according to the arrangement employed in the Brit- 

 ish Museum) is known by the manner in which the cells are arranged around an imagi- 

 nary axis, and connected with each other by flexible stalks. The general shape of the 

 whole group or " polyzoary," as it is termed by some authors, is very shrub-like, stand- 

 ing boldly erect, and giving out branches by two and two, after the fashion called by 

 botanists " dichotomous." 



Fig. A, Plate I., is an example of one of these beings, the LITTLE CHAIN, or BREAST- 

 PLATE, one of those beings that are so plentiful in the sea, and are properly called 

 zoophytes. This figure is of the natural size ; but in order to show the peculiarities of 

 structure, two examples of species belonging to the same genus are given as they appear 

 when considerably magnified. Fig. B is the Catenicella hastata, wherein is seen the 

 shape of the cells, the form of their mouths, the method in which they give out their 

 branches, and the peculiar organs called technically " avicularia " and " vibracula ; " the 

 former being processes that in many species bear an almost absurdly close resemblance 

 to the heads of birds ; and the latter, curious hair-like projections, which move regularly 

 backward and forward as if impelled by machinery. These remarkable organs will be 

 presently described more fully. 



The members of the present genus are found most commonly in the Australian seas, 



