404. 
Madeira, and the Canaries; but it is only in the Medi- 
terranean, especially in its Levantine portions and near land, 
that this strange genus becomes the commonest of countless 
forms that crowd the surface water. 
The general morphology of Doliolum has been described 
by Krohn, Gegenbaur, and Huxley; but its division into 
species must as yet be merely provisional, for its life history 
is far from complete. One large division of the genus has 
been traced only to the point where it commences its inde- 
pendent existence, on ceasing to be adherent, as one of the 
lateral series of buds from the gemmarium of its parent. 
The great majority of the specimens captured by me have 
differed in one or other particular from the forms described by 
the observers mentioned above ; one of the commonest types, 
for example, closely resembled D. denticulatum, but the 
fin-like frill round its proximal opening was either altogether 
unrepresented or replaced by two anteo-posterior or four 
antro-posterior and lateral tentacles, measuring about one 
sixth the length of the body, and presenting bulb-like points 
and bases. Sometimes, when the tentacles were only anterior 
and posterior, a pair, without enlarged points, sprang from 
the same dilated base. This variety of Doliolum, as well as 
many others, is not unfrequently marked along its sides with 
the magenta-coloured spots on the surface of the inner tunic 
enumerated amongst the characteristics of D. Miilleri. 
Two specimens recently captured near Malta differed 
from all the described forms in the structure of the gill- 
diaphragm dividing the internal cavity of the “ little barrel.” 
The ciliated perforations in this membrane, instead of being 
arranged in the usual bilateral series, were placed in pairs 
on the four sides of a lozenge-shaped space (see Plate XVIII, 
right division, fig. 2), through the hzemal angle of which the 
digestive canal passed. ‘The posterior or proximal orifice of 
the body was guarded by four tentacles, such as are described 
above; but in its general anatomy the little animal presented 
few other peculiarities, its eight muscular hoops, the twelve- 
toothed collar round its distal opening, the position and struc- 
ture of its ganglion, ciliated auditory (?) sac, endostyle, heart, 
and alimentary canal, being all in accordance with the usual 
type. Both the specimens captured measured about the one 
sixteenth of an inch, and both were furnished with germ-stems 
projecting—as in some of the varieties mentioned by Krohn 
—not from the hemal surface, but from a corresponding 
part on the ventral side (fig. 1 a). 
I have never been fortunate enough to find a Doliolum 
with a gemmarium sufficiently developed to exhibit the re- 
