THE NAUTILUS. 75 



In 1862, Cooper (5, p. 205) described a species Aeolis (Flabel- 

 lina ?) opalescens with an opaline color on the dorsal tentacles 

 and an orange stripe between them. Again in 1863 (6, p. 60) 

 the same author also records this species as Flabellina opalescens, 

 mentioning a pale variety with white-tipped branchiae (i. e. 

 papilla). 



Bergh in 1878 (1, p. 573) and again in 1879 (2, p. 81) 

 formed a new genus Hermissenda for this species. It is closely 

 allied to Phidiana but differs in the produced angles of the foot, 

 the form of the teeth, but especially in the absence of a hook on 

 the penis; and in these papers he identifies the Aeolis or Flabel- 

 lina opalescens of Cooper as Hermissenda opalescens, the only 

 member of the genus. The rhinophores are stated to be yellow 

 with an orange stripe between (cf. Eschscholtz). The papillae 

 are yellow with the purple-red liver diverticula shining through. 



Cockerell in 1901 (3, p. 122) also described the same form, 

 calling attention to the two " opal-blue" lines forming prac- 

 tically one, but dividing on the head and just behind it to ad- 

 mit ' ' a bright orange streak ' ' . He also mentions the ' ' broad 

 orange stripe on each side of the head", the fact that the 

 papillae possess an "orange subterminal ring" and that they 

 are " easily deciduous." 



The same author describes this species in conjunction with 

 Eliot in 1905 (4, p. 50) but strangely enough gives no reference 

 to his previous paper. This paper also mentions the "opal- 

 escent stripe down the back, bifurcating anteriorly so as to in- 

 clude an oblong area of bright orange." 



The first full account of the coloration of this species was fur- 

 nished by O'Donoghue in 1921 (8, pp. 201 and 202) but at the 

 time this paper was written the author has overlooked Cocker- 

 ell's paper of 1901 for the reason given above and had not ac- 

 cess to Eschscholtz' s Atlas. A second paper by the same author 



(9, ) deals with the range of color variation met with in 



the same species and also its spawn (11, ). In these two 



papers practically every point in regard to color mentioned in 

 Eschscholtz is also described; the opalescent line along the back 

 bifurcating at the front to include a bright orange area and then 

 passing on to the oral tentacles; the orange area on each side of 



