Royal Microscopical Society. 149 



tail, in the presence of a band of stigmata, in the occurrence of 

 only one branchial aperture, and in being smaller. One curious 

 2)oint the author makes out, is that the transparent outer tunic is 

 the commencement of the formation of the " Haus " described by 

 Mertens.* I had not the good fortune to meet with this curious 

 structure in a fully-developed form, but the constancy of the occur- 

 rence of the transparent tunic makes me doubt this interpretation 

 as applied to the present species. 



* 'Mem. Acad. St. Pe'tersbourg,' Q^" sOrie, torn, i., 1831. 



