1869.] CANADIAN ZOOLOGY. 423 



ited to the rhythmical contraction and expansion of the lunic, by 

 which water is continually introduced, and brings with it micro- 

 scopic organisms on which the tunicate feeds. The same action 

 subserves the function of respiration. 



In addition to the Boltenia,we have several species ot Cynthia 

 and Ascidia, one of which, Cynthia echinata, is remarkable for 

 its covering of stiff branching bristles. Another species, Didem- 

 nium roseum, exists in compound communities, encrusting sponges 

 and sea-weeds. Dr. Packard has dredged it at Hopedale, Labrador ; 

 and at Eastport, Maine ; and Mr. Whiteaves has found it at Gasp^. 



There are other species of smaller size, some of them highly 

 coloured, and others perfectly pellucid, so that the internal organs 

 are distinctly visible through the tunic, but all may be distin- 

 guished by the sac-like tunic and the two apertures. 



All the species found on our coast belong to the first sub-order 

 of Tunieates, that of the Ascidiae, which also includes the 

 remarkable Pyrosoniidae of the warmer seas, freely moving forms 

 in which the animals are grouped in radiating series in the walls 

 of a hollow cylinder, closed at one end : these creatures are said 

 to be impelled by the reaction of the water sent forth from the 

 excurrent apertures. 



A second sub-order, Biphora, includes the Salpidce, also inha- 

 bitants of the warmer seas, and floating in chain-like bands of 

 individuals, which, however, produce ova from which solitary 

 individuals are hatched, and these in turn develope within their 

 bodies colonies of banded Salpae. The Salpas and the Pyrosomas 

 are gifted with that luminosity in the dai'k which is the property 

 of so many marine animals. 



THE BRACHIOPODS. 



Of these curious and rare bivalve shell-fish, only a few species 

 are found on our coasts. The most common is Rhynchonella 



Rhynchonklla psittacea, Linn. Gulf St. Lawrence. 

 psittacea, the parrot's-bill Rhynchonella. (Fig 93.) It is a little 



