REPRODUCTION AND GROWTH 275 



the Beagle^ ch. ix., footnote) calculated 600,000 eggs for 

 a ribbon 20 inches long of a Falkland Island Dorid. 



The spawn of Jorunna johnstoni is in a spiral of four 

 coils with gracefully scalloped margins while that of 

 Lamellidoris inconspicua and L. depressa is a simple but 

 extensive spiral of 7 to 10 whorls. 



In many i^olids {Coryphella, Facelina, Molidia, also 

 Antiopella) the spawn is not only arranged in a spiral, but 

 the ribbon itself is zigzagged in its spiral course ; Cuman- 

 otus suspends a single cork-screw shaped coil by a long 

 thread. 



The forms of Nudibranch spawn are so distinctive that 

 recognition is easy. Those of members of the same genera 

 and families have generally speaking the same pattern (cf. 

 carnivorous Gasteropods). Kindred species may, however, 

 show very different degrees of elaboration in their work {e.g. 

 Lamellidoris hilamellata and L. depressa). 



Dorids with wide mantle margins are best adapted to 

 produce broad, flat ribbons because the egg-jelly is 

 compressed between foot and mantle and the undulations 

 of the edges of the ribbon, when they exist, are the counter- 

 part of the undulations of the mantle margin. On the other 

 hand, as we have seen, small animals, without any mantle, 

 such as the Limapontiidse, merely deposit short capsules. 



The egg-ribbon may be said to be composed of three 

 parts, as follows : — 



(i) General envelope enclosing all the eggs. 



(2) One or more envelopes enclosing groups of eggs in 

 strings or patterns. 



(3) Attachment jelly, which fixes the whole structure to 

 its support. 



Bolot, quoted by Eliot {loc. cit.)^ has given an interesting 

 account of the method of extrusion of the egg-ribbon in 

 Dorids. " The ribbon as it issues is soft and adhesive 

 but soon hardens in water. The Dorid 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 emergence of the ribbon is also due to an 



