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 Goniodoris 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 laminse 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 laminae 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 laminse 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 coronataj 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. bilamellata^ 

 with this difference, that the external lamina approaches the cy* 

 lindrical form with the ova arranged in the centre. The spawn 

 of the Dendronotus arborescent 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 Eolisvfo.^ deposited upon 

 the inner 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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