222 NATURAL SCIENCE. Sept., 



spiral of a coiled shell, whether foraminiferal or moUuscan, as due 

 rather to physical laws governing growth than to any advantage 

 which they might give their possessors in the struggle for existence. 

 The ingenious speculation that the pear shape of a guillimot's egg is 

 derived from the protection that it affords to the egg from falling 

 off the rock ledge, did not find favour v/ith Mr. Thompson, 

 who pointed out that the same shape was found in eggs, such as the 

 plover's, laid on the broad flat ground. This shape he ascribed to 

 the mechanical pressure exerted by a narrow oviduct on a relatively 

 large egg. 



Professor C. V. Riley, the eminent entomologist of Washington, 

 was prevented by the strict time-limits from properly presenting his 

 suggestive conclusions derived from a study of social insects. This 

 we hope partially to remedy by publishing his valuable paper 

 in extenso. Broadly put, his opinion was that Natural Selection 

 was an insufficient or impracticable cause in the evolution of the 

 varied groups of individuals met with in an insect colony, and that 

 much was due to the direct action of environment, notably of food. 

 These are views to which much attention has already been directed 

 in our own columns. 



Professor J. Berry Haycraft, who felt constrained to describe 

 himself as a physiologist, but not a biologist, raised a most interesting 

 objection to the views held by Weismann as to the part played in 

 evolution by sex. He pointed out that the conjunction of two 

 parents, instead of promoting variation, restrained it and kept it near 

 the mean. This, he said, was proved by the statistics collected by 

 Francis Galton; without sex, v/e should have no genera or no species, 

 only individuals. This interesting communication will appear in a 

 future number of Natural Science. 



Dr. F. A. Dixey contributed to the discussion a detailed account 

 of the evolution of mimetic characters in certain butterflies, without, 

 however, very clearly showing how the gradual stages that led up to 

 the completely mimicking forms could have been due to any struggle 

 for existence or any protective advantage. 



Professor H. F. Osborn, of Columbia College, New York, entitled 

 his paper, " Certain Principles of Progressively Adaptive Variation 

 observed in Fossil Series." A large part of it, however, was devoted 

 to emphasising the necessity for analysing variations according to 

 their character and the period of ontogeny at which they occurred. 

 Thus, he divided all variations into Palaeogenic and Neogenic, the 

 former being instances of reversion, and therefore not entering, like 

 the latter, into progressive evolution. Neogenic variations may again 

 be divided into four classes : — (i) Gonogenic, due to variation in the 

 original ovum or spermatozoon before their union ; (2) Gamogenic, 

 due to the union of diverse sexual elements ; (3) Embryogenic, due 

 to the influence of environment on the developing embryo; (4) Soma- 

 togenic, due to the action of habits or changed environment on post- 



