336 Transactions. — Zoology. 



out, no decomposition, so that the secretion must have taken 

 place with great rapidity. 



To give an idea of the frequency with which this imbedding 

 may occur, I may instance one collection of full-grown speci- 

 mens made at haphazard along the shores of Otago Harbour. 

 I collected between twenty and twenty-five specimens, and, of 

 these, five had these shellfish imbedded in the test of the 

 body. In all cases they were completely imbedded. This 

 frequency is above the average, but I have never yet gone 

 collecting in the harbour without getting at least two or three 

 BoltenicB with shellfish imbedded. I may mention that in 

 two or tbree collections on the open sea-shore among the 

 rocks I was unable to get any instances of it. The processes 

 may occur all over the body except on the dorsal surface 

 between the apertures ; their occurrence on the stalk is com- 

 paratively rare. In cases of complete imbedding the apex of 

 the process ends in a corkscrew-like arrangement. The 

 colour is generally more or less bleached out on the processes, 

 sometimes of a pure-white. In one instance I found two 

 shells imbedded in the same process. This shellfish belongs 

 to the family Mytilidee. In Brown's " Mollusca of the Firth 

 of Clyde " a very closely allied species — Crenella marmorata — 

 is spoken of as being found in the integument of Ascidia 

 Tnentula : it is there mentioned that over two dozen specimens 

 have been extracted from the test of a single individual. 



One of the most characteristic features of this species lies 

 in the very great thickness of the test, which, in ordinary 

 full-grown animals from Sin. to 4in. long, is from |-in. to Un. 

 The test is always thicker on the folds than on the inter- 

 spaces, the folds corresponding only in a slight degree to folds 

 on the surface of the body itself. 



c. Stalk. — The stalk is closely wrinkled transversely, is 

 twisted and creased, and rather tapering distad towards the 

 point of attachment. It may become thicker for short dis- 

 tances of its length than it is at the proximal end. It is of 

 a light-brown colour, and is often overgrown with seaweed, 

 sponges, &c. 



The stalk is generally round in section, sometimes com- 

 pressed, in some cases so much so that it becomes almost 

 ribbon-hke in appearance. The thickness, just as the length, 

 varies greatly: in full-grown specimens between 3in. and 

 4in. long it is between ^in. and ^in. 



In one specimen, in which the stalk, which was oblong in 

 section, was for a short distance of its length liin. broad by 

 fin. thick, I found imbedded a small shellfish. In another, 

 in which there was also a shellfish in the stalk, the stalk 

 had grown corkscrew fashion around the shellfish, and then 

 covered it with test-substance. In still another specimen, 



