MOSS’S POLYSTIGMATIC APPENDICULARIAN. 59 
to his ‘‘Challenger’’ Report,+ gives it an equally important 
place in his phylogenetic scheme, But with the increase 
of research, serious morphological difficulties have been 
seen to present themselves in the unique structure of the 
pharynx in this Appendicularian ; so that, subsequently, 
Professor Herdman appears to have entertained doubts 
with regard to the accuracy of the original description, and 
in his ‘‘ Revised Classification’? Mossia is referred to 
merely within the limits of a footnote. 
I have myself for some time held a theory in regard to 
the supposed peculiarities of Moss’s Appendicularian, and, 
as Increased experience has only tended to strengthen my 
view, | now venture to submit it to the notice of other 
zoologists. 
When the structure of Mossia, as indicated in the 
original description and figure, is compared with that of 
the other short-bodied Appendicularians (species of Oiko- 
pleura, Appendicularia, Megalocercus and Stegosoma), it 
is found to be peculiar in the following respects :— 
(1) The tail is very long, at least 54 times the length of 
the body, and at the same time slender and lanceolate; its 
lateral (morphologically dorsal and ventral) fin-like expan- 
sions are extremely small at the proximal end, and dilate 
very gradually, so that the tail does not attain its maximum 
breadth until a point some distance beyond the middle of 
its whole length. In all the above-mentioned Appen- 
dicularians, on the other hand, the tail is only about 3 or, 
at most, 4 times as long as the body, and reaches its 
ereatest breadth at a point almost immediately posterior 
to the region of its attachment to the body. 
(2) The mouth is a simple circular aperture without 
any projecting lips. In all the other forms under com- 
parison, with the exception of Appendicularia sicula and 
+ Third part, vol. xxvii., 1888, pp. 124, 125, 127, 149, 150. 
