SOME PUGET SOUND ASCIDIANS. 607 



test, and entire surface very clean. Color, transparent white. 

 Outlines of the zooids and the branchial orifices distinctly seen 

 on the surface. 



Zooids : Numerous closely set, evenly distributed, very much 

 contracted in all the specimens at hand ; disposed rather regu- 

 larly perpendicularly to the surface of the colony ; systems pre- 

 sent, though not conspicuous ; zooids in each not numerous. 

 Average length, as determined by measuring the depth to which 

 they reach in the test, about 6.5 mm., actual average length in 

 the contracted state assumed by nearly all the individuals about 

 2.5 or 3 mm. ; a few found with length as great as 4.5 mm. 



The long-pedunculate portion of the body between the thorax 

 and the gastro-genital mass which characterizes the zooids in 

 the normal condition, is wholly obliterated in the contracted 

 state (Fig. 32). 



Test and Mantle : Former without sand grains ; quite uniform 

 in texture, made up largely of bladder-cells, the small cells be- 

 ing comparatively few ; no vessels present. Mantle well devel- 

 oped, both longitudinal and circular muscle fibers being numerous 

 and strong. 



The ectodermal appendages given off from posterior portion 

 of mantle seem to be less prominent here than in most species 

 of the genus, though they are present. 



Branchial Apparatus : Branchial orifice easily distinguish- 

 able on surface of colony, the common atrial orifices rather ob- 

 scure. Both siphons prominent on detached zooid, the atrial 

 particularly long, though variable for different individuals ; both 

 with six well marked, broad, short lobes. Internal structure of 

 the thorax determined with much difficulty on account of the 

 heavy musculature of the mantle and the extreme state of con- 

 traction. Branchial tentacles apparently about twenty-four in 

 number, of moderate length. Endostyle heavy, closely tortu- 

 ous. Apparently five series of stigmata, though some uncer- 

 tainty here. 



Dorsal languets not seen. 



Digestive Tract : QEsophagus veiy long. Stomach and 

 intestinal loop proper forming a prominent mass at the extreme 



