ASCIDIA BOBUSTA. 81 



in consequence of the red colouring of the vascular 

 channels. In young specimens, however, it is some- 

 times of a uniform rose-colour, and in this state it is 

 pretty regular in form, and is attached by the whole 

 side. When full grown the test is remarkably rough, 

 hard, and thick, and frequently much distorted. The 

 larger specimens, obtained at Guernsey by Mr. Norman, 

 were firmly inserted between the roots of Laminaria 

 digitata, and so hard were the tests and their prolonga- 

 tions that they were with difficulty cut free with a 

 knife. The blood-channels in the test are more or 

 less of a red colour, mostly rounded and enlarged at 

 the extremity, and rather crowded. 



FIG. 15. Ascidia robusta. One half natural size. 



The mantle is more or less red in colour, sometimes 

 it is of a full rose-colour heightened towards the ori- 

 fices. The right or attached side is almost devoid of 

 muscular fibres, but on the other or free side they are 

 numerous, and as it were felted ; the tubes are long, 

 particularly the anal, which is turned backwards. 



The branchial sac extends only a little way behind 

 the visceral mass ; it is minutely plicated. The papilla? 

 are conical, not very wide at the base, and their apices 

 are rather sharp ; they are alternately large and small, 

 though nearly of equal length. The endostyle reaches 

 to the bottom of the sac. The oral lamina is not very 

 wide ; it is strongly ribbed transversely 011 both sides, 

 and has the margin slightly pectinated in advance "of 

 the mouth where it suddenly narrows ; in the neighbour- 

 hood of the mouth the pectinations are unusually long ; 



6 



