collected in a line along one margin, which may also be described as a string attached to
its support by a membrane along its whole length. In arrangement the string or ribbon
may be hung in an irregular festoon on seaweed, or arranged on a flat surface, sometimes
in the shape of a cup with the margin turned outwards (Ac/mthod/jris pilom)', or more
frequently in a spiral of varying completeness and complexity. -hatmllidoris bilameUata
lays a short spiral of one oj at nSbstytwo coils ; Boris ty&erwlata a large triple coil,
which may be as much as fifteen inches lodg when extended; Jorunna johnstoni a spiral
of four coils with elegantly scalloped margins; L. ineonspicua and L. depressa simple but
extensive spirals of 'UlSn to tem whorls.. But the spawn of many Solids {Corypltdlu,
Facelima, Jiolidia; also Antiopella) is not only arranged in a spiral ,:but the ribbon
or string is itself zig-zagged in its spiral course. Cwmqnotus suspends a single corkscrew
shaped coil by a long thread. The forms of spawn are, in fact, so distinctive that
the eggs of each species can usually be identified, and genera.and families are to a certain
extent characterized by the use of a particular arrangement or pattern. But generalization
in this respect is not very safe since widely different animals may agree in laying a single
coil, and kindred species' (LameUidoris Irilcmellata and L. depressa) may show very
different degrees of elaboration in their work. But, for mechanical reasons . lit would
seem that Dorids with wide mantle-margins are best adapted to produce broad flat
ribbons, because the flat shape is; maintained by compressing the mass of egg-jelly
between the' foot and mantle, and the undulation of the edges, when it exists, is the
counterpart of the undulations of the mantle-margin. On the other hand small animals
without any mantle, such as the Limapontiidaa, merely deposit short capsules. The
composition of the ribbon is often complicated, and it usually consists of at. least two
layers; (1) A general envelope enclosing all the“ eggs; (2) one or~~more envelopes
enclosing groups of eggs in strings or patterns. To these may be added the attachment
jelly which fixes the whole structure on its support. _
The formation of the ribbon in Doris twtereulata has been studied by M. Bolot.. It
takes place within the large organs known by the names of albumen and mucus gland.
The fertilized ova enter a canal in the centre of the first gland and receive a coating of
albumen poured on them from its walls, which are formed of ramified tubes. They then
go through narrow passages, where they receive a second envelope, which forms the eggshell.
1 Both these operations take place in the more opaque portion of the gland. The
eggs then traverse the twisted semi-transparenttubes which form the outer portion of the
gland and emerge embedded in a long string of jelly. This string falls into the central
cavity of the gland, where it is compressed by the flat walls and receives a final layer of
mucus, which constitutes the ribbon. Thus within the ribbon lies the much twisted eggstring,
and within that again the ova in a double envelope.3 As the ribbon issues it is
soft and adhesive, but soon hardens in the water. The Doris attaches one end to a
suitable spot and then begins to move slowly, thus aiding the exit of the ribbon by pulling
against the fixed point. But the exit is also due to an extrusive, movement in the glands,
1 This, of course, has nothing to do with the shell of the larva, which is secreted by a gland
formed in the larva itself.
8 Bolot, “ Sur la ponte des Doris,” Comptes rendus de l’Acad. des Sciences, Paris, 1886,
p. 829.
which can bb seen externally in a pulsating vesicle1 a t the opening of the oviduct,
which partly surrounds the ribbon and throbs rhythmically as it slowly pays it out. In
Doris Ivberculuta the rate of spawning is a little more than half an inch an hour.3 The
iibbon passes backwards on the right side of the animal between the mantle and the
foot, and thus recoivos a curve along the whole of its length, the concave side facing
outwards. The edge which lj||: nearest to the foot is attached to the rock, and the curl
of the spiral is counter-clockwise. Occasionally the curl is turned in the opposite direction,
but the other arrangement (counter-clock) is far t i | more frequent. The animals adopt
various attitudes when Spawning, but in some cases at any rate Dorids arch their lower
surface and stand over the ribbon as it issues from them. The spawn of British species
seems to be always white, at most tinged with rbse or |||llow, but some tropical Dorids
deposit very beautiful red or violet spirals, which look like flowers.
1 Observed by Trinchese uf.d by Hecht, who notices that it pulsates from twenty-four to fifty-six
times a minute.
8 Our specimen at Plymouth laid fifteen inches in twenty-four hours.