Z THE ENTOMOLOGIST S KECORD. 



all clearly understood, although there is no lack of theories regarding 

 individual cases. As a matter of fact, since the external forces which 

 go to make up the sum total of environment are so numerous, and in 

 many cases so diiierent, forming indeed combinations so varied that no 

 two environments are perhaps precisely similar, it must be evident 

 that each particular case must be judged on its merits, and that due 

 value must be given to all the available facts before an explanation of 

 any phenomenon can be considered as valid. It is with the intention 

 of suggesting explanations of two or three familiar phenomena men- 

 tioned by Professor Weismann that the following notes are offered. 



The Professor writes : "It is often assumed, without much proof, 

 that a certain variation of a living being is the direct consequence of 

 an external influence, simply because the variation in question is, in 

 fact, in some causal connexion with a definite external influence : sucli 

 an assumption is, however, founded on a totally false idea as to the 

 interconnexion of the phenomena. In many cases this will readily be 

 granted." The first illustration of this point which Professor Weismann 

 gives is the phenomenon of hybernation, a phenomenon, I need hardly 

 say, of the greatest interest to entomologists. " Suppose for instance 

 that we assert," he says, " that cold is the actual cause of the winter- 

 sleep of marmots. It is clear that this statement is incorrect, and that 

 not the cold, but the peculiar organisation of the marmot, causes the 

 reaction of hybernation : cold cannot throw a dog or a bird into a state 

 of slumber for the winter. We are here, therefore, concerned with 

 a special adaptation of the organism to a stimulus — cold — which affects 

 it in such a manner that it escapes from what would otherwise be a 

 destructive influence. We are unable to demonstrate with a microscope 

 the fine ' molecular ' or histological variations in the nervous and other 

 systems on which the capacity for hybernation may depend ; but some 

 such modifications must exist, and they cannot be regarded as a direct 

 effect of the cold, but must rather be looked upon as arrangements to 

 counteract its influence." 



Suppose for the moment that we grant this hypothesis. Then of 

 course heat is the external stimulus which causes the peculiar organi- 

 sations of those animals that sestivate to respond in such a manner to 

 its stimulus as to produce the phenomenon of aestivation — a term 

 applied to that state of torpidity assumed by certain animals in tropical 

 countries, and extending in their case through the period of greatest 

 heat. Now, I would ask, is cold the external stimulus which induces 

 in certain animals the reaction of their tissues that produces the pheno- 

 menon of hybernation ? Is heat the external stimulus which induces 

 the reaction known as sT^stivation ? Are there other stimuli which aid 

 cold or heat in producing these reactions ? Has selection stepped in 

 and made a much more complete set of stimuli necessary for the pro- 

 duction of these phenomena than the Professor appears ready to grant ? 

 Presuming that these phenomena enable the animal to escape from 

 "what would otherwise be a destructive influence," is the special 

 reaction of the organism to "cold" or "heat" suificient to account for 

 the phenomena ? 



We all know that, long before the period of hybernation commences, 

 long before the stinnilus of " cold " can in any way acton the oi-ganisa- 

 tion of an animal, other stinn;li affect liybernating animals in a very 

 marked manner. Such stimuli cause the animals to eat a quantity of 



