170 THE entomologist's record. 



principles in mind, let us proceed to a consideration of the papers 

 before us. 



Mr. Tutt begins by a discussion of certain statements made by 

 Professor Weismann in his Romanes Lecture at Oxford, " On the 

 Effect of External Influences upon Development." The professor is 

 insisting upon the distinction to be drawn between such changes in 

 the individual organism as are the immediate and direct result of a 

 change in external conditions, and such as only indirectly follow an 

 alteration in the environment ; such changes, in fact, as are really 

 due to, and characteristic of, the already existing constitution of the 

 organism, and only need an external stimulus of whatever kind to 

 set them going. As an instance of the latter species of change he 

 adduces the hibernation of the marmot, which, as he points out, is a 

 phenomenon immediately dependent on the intimate structure peculiar 

 to the tissues of the marmot, as distinct from non-hibernating 

 mammals ; and not on the external circumstance of cold, which 

 is in itself, as we see in the case of ordinary mammals, powerless 

 to produce the winter sleep. Cold, however, Weismann implies, 

 though not the cant^a i'[ficiens of hibernation, constitutes, in the 

 case of the marmot, the requisite external stimulus for the assumption 

 of that condition ; to use a figure familiar to logicians, it supplies 

 the flrst link in the chain of causation, or pulls, as it were, the trigger 

 of the already loaded gun. 



To these statements Mr. Tutt objects that cold cannot be the 

 actual stimulus inducing hibernation, inasmuch as the winter sleep 

 itself is merely the last term in a complex series of changes, and these 

 begin with the ingestion of unusual quantities of food before the cold 

 period has yet arrived. It is possible that Mr. Tutt may be right 

 in supposing that cold is not in this case the actual stimulus which calls 

 into play the characteristic winter slumber ; but the point is of small 

 importance, for Weismann's only contention with regard to hiberna- 

 tion is, that cold is at best a stimulus, giving, so to speak, the signal 

 for action to the already prepared organism.*'' Cold is not the 

 immediate cause of this physiological condition, and might without 

 damage to Weismann's argument be even denied the function of a 

 stimulus. It must, moreover, be carefully borne in mind that 

 Weismann is here only referring to the relation of the cold of any 

 one autumn in the life of a marmot, to the hibernation which is 

 entered upon at that particular time by that actual individual. He 

 would, of course, not think of denying that the organism of the 

 marmot has become adapted for hibernation under the operation of 

 natural selection, in order to meet the vicissitudes of environment 

 caused by a periodical accession of cold. 



Turning from the case of the marmot, Mr. Tutt recalls to our 

 recollection various interesting instances of hibernation in the lepi- 

 doptera, which are quite enough to show that, however the case may 

 be Avith the hybernating mammal, the assumption of the like condi- 

 tion in insects is not necessarily dependent on the action of cold as a 

 stimulus. The case of V. urtirar is a specially interesting one, inas- 

 much as it affords evidence of a kind of physiological dimorphism, 

 if the expression may be allowed, within the limits of the same brood. 



* See a re-statement of the same position by Weismann, " Neue Versuche, etc." 

 Zool.Juhrh. Jena, 1895. 



