212 Mr. N. Colgan — Contributions towards a 



longitudinal series. Each papilla contained a well-developed 

 hepatic lobe, which extended almost to the apex of the 

 papilla. The body of the animal ended behind in a long and 

 depressed tail similar to that of the Eolididae. There was no 

 trace of a caudal fin. 



The first modification which appeared in the form of the 

 animal was the lengthening of that portion of the body com- 

 prised between the first and the second of the dorsal papillae. 

 Next, the base of the Brat papilla swelled up, forming a semi- 

 lunar curved cushion with the concavity turned towards the 

 rhinophore. Little by little this cushion completely embraced 

 the rhinophore and increased in height until it enveloped the 

 lower two-thirds of that organ, and thus formed its sheath. 

 The upper third of the first dorsal papilla, whose lower two- 

 thirds had been transformed into the sheath, preserved its 

 shape and its orange-yellow colour and formed the posterior 

 papilla of the sheath-margin. Then four other papillae 

 sprouted out (" spuntarono ") from this sheath-margin. 



Meanwhile that portion of the body lying between the 

 second and the third of the dorsal papillae and that between 

 the third and the fourth lengthened day by day, and at the 

 same time the bases of these papillae became depressed from 

 without inwards, and from the free margin of the depressed 

 part sprouted small papillae. Finally, the lower two-thirds 

 of each papilla were transformed into a triangular arched 

 membrane with the concavity turned outwards. The upper 

 angle of this membrane was formed of the upper one-third of 

 the original papilla, which had retained its primitive form 

 and its yellow colour. 



The membranes formed from the inferior region of the 

 primitive papillae of each side of the animal became fused 

 together, and at the same time there appeared at each side of 

 the tail a longitudinal eminence, a fold of the skin in con- 

 tinuation of the membranous base of the last papilla. These 

 folds grew in height and assumed a triangular form, and, 

 meeting near the apex of the tail, formed the caudal fin. 



These facts, concludes S ignore Trinchese, shed a vivid light 

 on the phylogeny of Lomanotus, and demonstrate its descent 

 from an ancestor having the form of an iEolid. 



1889-1890. — Mr. W. Garstang, in a paper on the 

 Nudibrancliiate Mollusca of Plymouth Sound, published in 

 vol. i. of the 'Journal of the Marine Biological Association 

 of the United Kingdom,' records two captures of Lomanotus 

 at Plymouth, one of three specimens ranging from £ to f 

 inch in length made in 1889, another of eight specimens 



