184 IANTHINID.E. 



koo-like) laid its eggs there. According to Philippi 

 (Handbuch, p. 179) the fry of /. communis, before it 

 is excluded from the matrix, has an operculum, and its 

 velum or hood is furnished with vibratile cilia and two 

 large black eyes. Embryonic shells of this species and 

 of /. rotundata which I have examined under a micro- 

 scope are nautiliform, of a yellowish-brown colour, and 

 resemble in shape those of Stilifer. I could not discover 

 an operculum in any of the specimens, although the 

 mouth was closed by a film of dried animal matter. The 

 Ianthina, when irritated, discharges a beautiful purple 

 or violet-coloured liquid in considerable quantities. 

 Captain Cook observed that each individual yields about 

 a tea-spoonful. This liquid, says Mr. Adams, " is at 

 first equally diffused, but shortly sinks to the bottom in 

 the form of a deposit, leaving the water pellucid. The 

 bag or reservoir containing the colouring- fluid is visible 

 through the skin on the back of the neck ; and the fluid 

 is poured direct into the branchial cavity, and makes its 

 escape from under the free edge of the mantle. My 

 dyeing operations with this purple fluid were not crowned 

 with success, the beautiful colour fading gradually away, 

 leaving magenta and mauve yet possessors of the field." 

 It was suggested, in a review of the first volume of the 

 present work, which appeared in the ' Parthenon ' of 21 

 June 1862, that the colour of this fluid is due to chloride 

 of gold, and that the secretion is of a poisonous nature. 

 I am no chemist ; and I regret that my literary glean- 

 ings have not enabled me to solve the former problem. 

 The origin of the colouring-matter of shells and other 

 animal productions, as well as of that of vegetables, 

 seems to be involved in nearly equal obscurity. Liebig 

 attributed the red and blue colours of flowers to am- 

 monia; but whence is the ammonia derived? We 



