TRANSACTIONS OF SECTION D. 689 



2. On the Sensitiveness of the Boot-tip. By Professor W. Pfeffer. 



3. Exhibition of Diagrams. By Professor L. Kny. 



MONDAY, AUGUST 13. 

 Department of Zoology. 

 The following Report and Papers were read : — 



1. Interim Report on Telegony, — See Reports, p. 346. 



On some Difficulties of Dartvinism. 

 By Professor D'Ahcy Thompson. 



3. On Social Insects and Evolution. By Professor C. V. Riley. 



Experiment and discussion on the question as to whether acquired characters are 

 transmitted or not through heredity have of late heen largely based upon the 

 economies of insects, and especially of the social species. The author gives a 

 summary of what is known of the habits and economies of bees, wasps, ants, and 

 termites, especially as to the development of the young. He points out that the 

 origin of neuters, with their dlversitied forms, in these social insects has been con- 

 sidered one of the greatest difficulties with which the theory of natural selection has 

 had to contend. Weismann, in urging his own particular theories to account for the 

 variation which organisms have undergone, insists, and has, within the last year, 

 in his controversy with Herbert Spencer, emphasised his belief, that these neuter 

 insects absolutely preclude the idea of the transmission of acquired characters. 

 The author believes, on the contrary, and endeavours to show, that while these 

 neuters among social insects, with their varied structures and habits, do indeed oflfer 

 serious obstacles to the theory of natural selection as an all-sufficient theory to 

 explain the phenomena, these are nevertheless perfectly explicable upon the general 

 principles that have governed the modificaticm of organisms, among which natural 

 selection plays an important but limited part. 



Among the social Hymenoptera, where, as in the bees and wasps, the larva is 

 nursed and brought up in a definite cell or cradle, the three castes of male (or 

 drone), fertile female (or queen), and neuter (or worker) are quite definitely fixed 

 and separated. The difierences between the worker and the queen are, however, 

 solely due to the treatment of the larvre, and are consequently under the control of 

 the colony. The same larva, according to treatment and nurture, may produce 

 either a perfect queen or a worker, between which the diflFerences as to size, struc- 

 ture, external and internal organisation, and length of life are very great. This is 

 absolutely and definitely proved for the bees, and is doubtless equally true, though 

 with less absolute proof, of the wasps, in which the same three castes of male, 

 female, and neuter obtain in some species, while in others the neuters are replaced 

 by parthogenetic or unimpregnated females, normally capable of reproducing. In 

 the ants, where the larva is not confined to a definite cradle, and where there are, 

 in the more typical species, two castes of neuters, viz., soldiers and workers, the 

 variation between the different castes is greater, and there is also more variation in 

 the individuals composing the different castes ; but the evidence all points to the 

 fact that these different individuals are also the result of food and nurture, very 

 much as with the bees and wasps. 



In the three families of social Hymenoptera above mentioned the young are 

 maggot-lilfe and absolutely helpless and dependent on the nurses. In the termites, 

 1894. TY 



