I. InTRODUC'TIOX. 



A CONSIDERABLE part of tliis work was done under the 

 direction of Professor Trevor Kincaid, at the University of 

 Washington (Seattle), 1914-15. It was continued at Columbia 

 University, 1918-20, and at AA'oods Hole, 1919 (summer). 

 Dr. T. C. Frye, the Director of the Puget Sound Biological 

 Station at Friday Harbour, Washington, had some new material 

 collected during the summer of 1919, and sent to me at Woods 

 Hole. Upon this material, and the previous data together with 

 new material collected at Friday Harljour, during the summer 

 of 1921, this paper is concluded. 



In three previous communications (1919, 1921) I described 

 the method of feeding, the kind of food, method of swimming 

 (1922), and the colour, of Melibe leonina (Gould) as well 

 as the distribution of the family T e t h y m e 1 i b i d a e ^ Bergh 

 (1890, 1892 : 1039-43). I also made an extensive review of 

 the literature on the nudibranchiate molluscs, particular!}' the 

 C 1 a d o h e p a t i c a . Several misprints, relative to year, volume, 

 and page, occurred in the literature. These have been corrected. 

 I hope that the references as printed in my papers maiy be of 

 help to other workers in this field on the molluscs. 



^ Attention should be called to the fact that the name Tethys as 

 applied to a Nudibranch is incorrect. This was established in 1895. 

 (Vide H. A. Pilsbry, " Classification and Phytogeny of Tectibranchiata ", 

 ' Manual of C'onchology', 16: i-vii, 1-262, 74 plates.) The name Tethys 

 was tirst given to a Tectibranch by Linnaeus. (Vide 'Systema Xatura', 

 lOth Edition, 1758, p. 653.) Consequently the familyname Tethymeli- 

 b i d a e must be rejected from the nomenclature of N u d i b r a n c h i a t a . 

 The Nudibranch 'Tethys' has apparently no name of its own. 



