274 THE BIOLOGY OF THE SEA-SHORE 



Nudibranchs has been extensively studied by Eliot [op. cit.), 

 from whose valuable monograph most of the following 

 details are taken. 



No elaborate precautions are taken by this family of 

 molluscs to conceal their eggs, a circumstance which is 

 probably amply compensated by their enormous fecundity, 

 as noted earlier in this chapter. Sometimes the strings or 

 ribbons containing the eggs are left in conspicuous positions ; 

 sometimes they are placed in surroundings where they are 

 not noticeable or in sheltered nooks such as the under side 

 of rocky ledges. But in all cases the eggs are enclosed in 

 some sort of case. 



The simplest form of egg-case is a rounded capsule 

 such as that laid by the Limapontiidae ; Galvina exigua 

 hangs oval masses of bright white on seaweed ; Tergipes 

 despectiis deposits its eggs in kidney-shaped capsules. 



Many small Solids, e.g. Amphorina aurantiaca and 

 A. olivacea, deposit spawn in a single imperfect coil, roughly 

 crescentic in shape, and the spawn of some Polycerids, e.g. 

 Polycera quadrilineata and Ancula cristata, is much the same. 

 Other genera, however, both of Solids and Dorids, produce 

 more complicated patterns. The spawn may be a simple 

 string, or a ribbon with eggs collected along one margin, 

 which may also be described as a string attached to its 

 support by a membrane along its entire length. In arrange- 

 ment, 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 

 {Acanthodoris ptlosa)y or more frequently in a spiral of varying 

 completeness and complexity ; Lamellidoris bilamellata lays 

 a short spiral of one or at most two coils. The eggs of 

 Archidoris tuherculata, perhaps the commonest shore Nudi- 

 branch, are laid in a large triple coil, according to Eliot, some 

 15 inches long. Colgan (1914) states that four coils taken 

 at Bullock and Dalkey Island in April, 1914, were, when 

 opened out, 32, 28J, and 17 inches long respectively, the 

 breadth being from f inch to i J inches. The number of ova 

 in the largest was calculated at 645,000. Darwin {Voyage of 



