8 Tun. 
TUNICATA. 
the atrial cavity, with its two short tubes opening into the branchial sac ; 
(2) the presence of a neural tube running along the whole length of the 
body, and having cephalic and visceral terminal enlargements cor¬ 
responding to the cephalic and caudal ganglia of Appendicular ia ; and 
(3) the position of the anal aperture on the surface of the body. He 
points out the similarity between the life-history of Anchinia , so far as it 
is known (the asexual form, or “Nurse,’ 5 has not yet been observed), 
and that of Doliolum. In both cases the sexual generation is poly¬ 
morphous, and has three forms, two of which remain in a rudimentary con¬ 
dition, so far as the reproductive organs are concerned. In the case of 
Anchinia , however, the three forms are not found together on one stolon or 
outgrowth, as in Doliolum, but are produced successively ; and, moreover, 
in Anchinia the reproductive zooids of the sexual generation are not borne 
by the second form of sterile zooids (the foster-zooids), but are produced 
independently. 
Herdman (9) gives an account of the structure of the sexual genera¬ 
tion of a species of Doliolum ( D . denticulatum ?) found in large numbers 
in the North Atlantic during the cruise of the ‘ Triton ’ in 1882. 
Traustedt (26) discusses the Salpidce, giving a synopsis of the family, 
and describing fully the solitary and the aggregated forms of 11 species 
and 1 new variety ( Salpa democratica-mucronata var. flagellifera) , with a 
detailed synonymy. 
