ee ae. 
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Ova of the Nudibranchiate Mollusca. 379 
nata and Polycera quadrilineata is of a ribbon-shape and of a 
white colour, adhering by one of its edges to the substance upon 
which it is deposited ; while in the Gontodoris Barvicensis, Den- 
dronotus arborescens and in the Eolis, it assumes more or less the 
shape of a rounded chord. The ribbon-shaped spawn of the 
Polycera quadrilineata formed a small segment of a circle, and 
measured between half an inch and an inch in length, and about 
three-twelfths of an inch in height; that of the Doris bilamellata 
a large segment of a small circle, measuring in some cases eight- 
twelfths of an inch in height ; while that of the Doto coronata, 
wound in a spiral manner round the branch of the zoophyte to 
which it adhered, and its free edge, instead of being straight as 
in the other ribbon-shaped spawn mentioned, presented under the 
microscope numerous and regular convexities. The spawn of the 
Doris bilamellata consists of two laminze of a structureless sub- 
stance, between the layers of which, except for a small space near 
the edges, very numerous small ova are placed. These ova are 
firmly fixed in their position by a substance of the same nature as 
the external Jaminz which unites them together, and fills up the 
interstices among the ova. The ribbon thus formed is very elastic 
and tough, but when the ova are about to escape it becomes soft 
and gelatinous, the lamine separate at the edges, and at a later 
period may give way at different parts. This description applies 
to the spawn of the D. tuberculata and Doto coronata, and. pro- 
bably also to the Polycera quadrilineata, but my notes do not 
enable me to speak positively of this last. The spawn of the 
Goniodoris Barvicensis is either white or of a faint pink colour, 
has a disposition to assume the semicircular form, and some 
portions were from one to two inches in length, and from a 
quarter to nearly half an inch in circumference, and though 
rounded, it shows a slight tendency to the ribbon form. Its 
structure is essentially the same as that of the D. bilameilata, 
with this difference, that the external lamina approaches the cy- 
lindrical form with the ova arranged in the centre. The spawn 
of the Dendronotus arborescens was in the form of a small, long 
and waving chord, destitute of the strength and elasticity of the 
ribbon-shaped spawn, of a faint pink colour, attached to a branch 
of a Plumularia, along the side of which it formed a series of fes- 
toons. ‘The circumference of this chord was formed of a trans- 
parent membranous-looking substance having no distinct struc- 
ture, and the ova which occupied the interior were easily displaced 
and forced outwards. The spawn of the Holis was deposited upon 
the imner surface of the vessel in which it was kept and upon a 
stone, and consisted of a small chord of a pale pink colour about 
one-twelfth of an inch in diameter, arranged in a close spiral form, 
the turns of which lay almost in apposition, and were surrounded 
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