MOLGULA CONGHILEGA. 



the Ascidia- conchilega of Miiller. We are glad to find 

 that the late Professor Sars was also of opinion that 

 A. conchilega is a Molg-nla. Of two specimens sent to 

 us by Professor Loven under this name, both covered 

 with shelly fragments, and not to be distinguished 

 from each other in external appearance, we found on 

 dissection that one was a Molgula of this species and 

 the other a true Ascidia. A Cynthia, too, C. glacialis, 

 is in like manner invested with fragments of shells, 

 and scarcely distinguishable from these externally, so 

 little can external characters be relied upon in this 

 family, even in generic points of view, when the 



. 



FIG. 36. Part of branchial sac of Holgula conchilega. Much enlarged. 



apertures are concealed. All three were unattached. 

 The specimens received from the late Professor Goodsir 

 were covered with largish fragments of shell ; those 

 obtained on the Northumberland coast are more 

 commonly clothed with mere sand, sometimes having 

 minute shelly matter intermingled. The size of the 

 particles of this extraneous coating depends on the 

 accidental condition of the kind of sea-bottom on which 

 the specimens occur, as might be expected, for there 

 is not anything to show that the animal has the power 

 of selecting these fragmentary matters, but on the 

 contrary it appears that it attaches indiscriminately 

 those amidst which it happens to be placed. 



