MORPHOLOGY OF MELIBE 513 



Since the descriptions of Gould and also of Cooper and Fewkes, 

 each of whom described a species from the American west 

 coast, are rather incomplete, and since the anatomy had not 

 been worked out, I felt that there was sufficient reason to 

 engage in such an investigation upon this very interesting 

 animal. As a result of this work I have succeeded in bringing 

 to light some points of considerable zoological interest. 



The body-substance of Melibe leonina appears as a 

 mass of brown jelly, when the animal is alive or freshly caught : 

 in the aquarium it turns practically transparent ; Avhen it 

 has been preserved in alcohol or formaldehyde it gradually 

 loses its brown colour, and becomes almost white. O'Donoghue 

 (1922: 125) says: 'Hundreds of individuals of this species 

 have been seen, but there is practically no variation in colour. 

 In some forms the yellowish or whitish-grey jelly-like body 

 may be tinged with pale brown but hardly sufficient to notice.' 

 However, while this is really the general colour of Melibe 

 leonina, I have also seen it deep green in colour (vide 

 Agersborg, 1922 a: 439-42). Gould (1852), in his original 

 description of this species, says : ' Body limaciform, smooth and 

 of a pearly and whitish colour, finely reticulate with orange.' 

 The colour of the animal is caused by an extensive ramifica- 

 tion of the brow^nish-coloured liver in the body-w^all (Pis. 1 and 

 30, figs. 1, 2, 4, 7, 18-23, 25) ; a ramification which extends 

 to the hood, the tentacles, the papillae, and to the ectoderm 

 of the rest of the body. The colour of nudibranchs has some- 

 times been attributed to their food, Hecht (1895), Eliot (1910) ; 

 but Alder and Hancock (1845) ascribe the colour to the liver 

 and the gonads. Bergh (1879a: 163, 165), describing Melibe 

 vexillifera, says in fact: ' Durch die dtinnen Korper- 

 wande schimmerten, besonders an den Seiten, die denselben 

 angehorenden, dicht an einander liegenden, schmalen, weiss- 

 lichen, parallellaufenden Langsfasern hindurch ; ferner undeut- 

 lich die Eingeweide, besonders Theile der Leber und die 

 vordere Genitalmasse ; . . . Die Leber wie bei anderen Meliben 

 eine lose, gelblichweisse Masse, welche vorne an den Magen 

 reicht, hinten sich bis an das Ende der Eingeweidehohle 



NO. 268 M m 



