850 MB. W. BATESON ON THE [DeC. 3, 



view of their physiological identity, though perhaps morphological 

 non-correspondence. 



On the other hand, the last mentioned suggestion is not certain, 

 especially in view of a statement of Mayer upon the lung-muscle 

 of Pipa, which I have quoted in my paper upon that Amphibian. 

 Mayer refers to the origin in Pijpa of a lung-muscle from the 

 ihuin which I have not found myself, but which corresponds with 

 what I have found in Xenopus. Apart, however, from the lungs, 

 there is so great a resemblance between the entire musculature 

 which goes to form what I have ventm-ed to term the diaphragm, 

 that I cannot look upon it as a case of convergence due to similar 

 physiological needs. The only possible test for discriminating 

 between morphological resemblance and a likeness due to similar 

 needs woidd appear to be the complexity of the structures in 

 question. Judged by this test, I am inclined to regard the new 

 facts put forward in this paper as evidence of relationship between 

 Xenopus and Pipa. 



3. On the Colour-variations of a Beetle of the Family 

 Chrysomelidce, statistically examined. By W. Bateson, 

 M.A., F.R.S., Fellow of St. John's College, Cambridge. 



[Eeeeived December 3, 1895.] 

 (Plate XLVII.) 



At a meeting of the Society on May 1, 1894, I exhibited living 

 specimens of Gonioctena variabilis in illustration of the remarkable 

 range of colour-variation in the species. Since then I have had 

 opportunities for a fuller investigation of the matter, and the 

 following paper is an account of the results obtained. 



G. variabilis * is a small beetle, about | in. long, belonging to the 

 family Chrysomelidae. It Hves on Spartium retama, a plant allied 

 to the Common Broom, very generally distributed in hilly places in 

 the south of Spain, though absent, I believe, from the hmestone 

 districts. This plant grows as a bush varying in height from one to 

 about seven feet according to the situation, humidity, and exposure. 

 The stunted form is dense and compact, having stout branches 

 spreading out more or less horizontally, giving ofE erect leaf-bearing 

 stems set closely together. The tall form is slender and graceful, 

 and its leaf-bearing stems are generally pendulous and wavy. In 

 their extreme forms these two conditions of the plant differ con- 

 siderably from each other, but all intermediate conditions are found. 



In colour the stems of this Spartium are of a dull greenish grey. 

 The surface is marked with irregular longitudinal ribbings, \^hich 

 give it an appearance of faint striping. It is upon the stems of 

 this plant that the beetles live, infesting both forms indifferently. 

 "When at rest they are commonly seen sitting with their heads in 

 the axils of the twigs, their bodies being closely pressed against 



1 The genuB Go7iioctena is Phytodecta of the Munich Catalogue. The species 

 G. variabilis is the Phytodecta (sgrota of Fabr. and Suffr. 



