THE PHYLACTOLJQMATA. 369 



Pig. D represents a sprig of the Bowerbankia imbricata of the natural size, and the 

 same species is shown much magnified at E. In this species the cells are also placed 

 upon the footstalk formed by the polyzoary, but they are not grouped together as in the 

 last-mentioned species. The polypes are long and slender, and the walls of the cells are 

 delicately transparent, thus allowing the observer to examine the structure of the polype 

 through the walls. 



A part of the digestive organs of the Bowerbankia is deserving of a passing notice. Like 

 all the other species, it possesses a feathery crown of tentacles sprouting around the mouth, 

 and directing the minute objects which serve it for food, from the mouth into the oesophagus, 

 popularly called the gullet. In this genus, however, a further provision is made, for immedi- 

 ately below the oesophagus comes a kind of contractile gizzard, lined with a marvellous pave- 

 ment of teeth arranged in a tesselated formation, and capable of bruising and crushing the 

 food before it is passed into the stomach and thence to the intestine. One species of this 

 genus, Bowerbankia densa, is common on the English coasts, being found parasitic on Flustra 

 foliacea in patches of about an inch or so in diameter, and may be readily obtained by those 

 who are desirous of studying its habits and structure. 



At Fig. F is given a small portion of a polyzoon named Buskia nitens, the former title 

 being in honor of the eminent naturalist, and the latter alluding to the shining appearance of 

 the species. 



WITH the next descriptions our examples of the Marine Polyzoa are terminated. 



Of the Alcyonidium gelatinoswn, popularly called the Sea Ragged Staff, Mermaid's 

 Glove, or more commonly, Dead Man's Fingers, in allusion to the cold dampness of its 

 surface, great numbers can be found on the sea-shore, especially after a storm, when it may be 

 seen lying among the masses of sea- weed and other debris that are flung on the beach by the 

 angry waves. In its natural state it is affixed by its base to stones, shells, and other supports, 

 and is always extremely irregular and variable in its form, no two specimens being alike. 

 When picked up, its aspect is anything but attractive, but when placed in sea-water and 

 suffered to remain at rest for a while, it becomes a most beautiful object. From each of the 

 tiny pits with which its surface is thickly studded, projects a polype, with a beautiful crown 

 of waving tentacles, and so numerous are these polypes, that they densely cover the surface 

 and render microscopic observation rather difficult. 



As in other species, fresh colonies of the Alcyonidium are formed by gemmules, which are 

 given forth from the general mass, swim about freely for a time, by means of the cilia with 

 which their surface is thickly studded, and when they have attained a proper age, settle down 

 and at once begin to develop fresh cells on all sides. The little vesicles wherein the gemmules 

 are originally formed, may be seen in the spring scattered through the transparent substance 

 of the polyzoary, and looking like little white points. Each vesicle contains about five or six 

 geramules, and as it can be easily isolated, its rupture and the consequent escape of the 

 gemmules can be easily seen in a moderately powerful microscope. 



Our next ample is the Pedicellina echinata. These little creatures look wonderfully like 

 the common moss that grows so plentifully on walls. The cilia by which the necessary 

 currents are formed in the water for the purpose of obtaining food, is similar to a tulip in its 

 form. 



PHYLA CTOL^EMATA. 



ONE of the most remarkable polyzoa that at present are known to exist, is the Oristatella 

 mueedo. The entire polyzoary is not only free and unattached to any object, but even 

 possesses the power of locomotion. It is frequently seen to crawl over the stem of some 

 aquatic plant. In order to qualify it for this process, the lower surface of the polyzoary is 

 modified into a flattened disc, which thus becomes analogous to the foot of the gasteropodous 

 mollusks already described. The substance of the disc is contractile. 



VoL.lII.-17. 



