N0T0PTER0PH0RUS. 143 



Found by the late Mr. Albany Hancock in the 

 branchial sac and water-passages of Ascidia mentula 

 from Shetland, and more recently by the Rev. A. M. 

 Norman in Ascidians from Oban, Loch Fyne, and 

 Herm (Channel Islands). 



My knowledge of this species is derived entirely 

 from M. Hesse's memoir, and from specimens kindly 

 given and lent to me by my friend the Rev. A. M. 

 Norman ; but owing to the long immersion of the 

 animals in spirit I have not been able to observe 

 satisfactorily many of their characters, especially 

 those of the delicate membranous wing-like expan- 

 sions, which, when exposed to the action of alcohol, 

 become shrivelled, opaque, and shapeless. I therefore 

 give a short abstract of M. Hesse's description : — 

 These expansions, which are six in number, are mem- 

 branous, flat, papillose, hyaline, contractile, and fixed 

 by the base to different parts of the body. The first 

 is triangular, divided at the extremity into long 

 lashes, and fixed to the back of the neck, forming a 

 sort of hood for the protection of the head ; the other 

 four expansions are lateral, placed two at the base of 

 the neck, the other two at the middle of the second 

 thoracic segment ; they, especially the second pair, are 

 much larger than the first, and are also divided into 

 lash - like extremities. These appendages, closely 

 resembling in general effect the wings of a butterfly, 

 are, of course, not used in the same way, but are 

 nevertheless moved with considerable energy by 

 means of the powerful muscles to which they are 

 attached, and they are endowed at all points with a 



