194 THE entomologist's keoord. 



also transmissible. This was Darwin's main plank in his theory of 

 " natural selection" ; and even when he brought forward examples 

 based more directly on Lamarckian principles, and assumed that 

 the environment had developed modifications which were trans- 

 missible, we find him always going somewhat farther and attempting 

 to prove the influence of " natural selection " in such cases. 



We can see how great a step this is in advance of Lamarckism pure 

 and simple. The latter assumed a direct modification due to varying 

 external conditions ; the former explained how it was possible for the 

 external conditions to become tlie stimuli which set in motion ten- 

 dencies to variation already existing in the organism itself. It did not 

 pretend to prove the development of new organs (or of ac(|uired 

 characters as recent writers choose to term it), but it showed how 

 modifications of existing organs were slowly brought about and became 

 transmissible. The organ, being a part of the animal, was clearly 

 transmissible, the form it assumed has already indicated its tendency 

 to develoj^ on given lines, and hence there appears no difficulty in 

 understanding why it took the direction. To talk of the transmission 

 of a slowly- changing but existing organ as the transmission of an 

 acquired character, or to put such a development on a par Av^itli the 

 mutilation of a given structure to test whether the mutilation will be 

 transmitted as an acquired character appear equally absurd. 



But we are not now particularly concerned with the question 

 whether acquired characters can or cannot be transmitted, although Dr. 

 Mivart appears to consider that this question has some bearing on the 

 transmission of modified existing structures. We believe the latter to 

 be quite i)0ssible, whether it be explained by " natural selection " 

 weeding out the useless in the particular line of development in tlie 

 animal in Avhich such modification be found, or whether it be 

 explained by Weismann's theory that, although structures themselves 

 are not transmissible, the peculiar characteristics of each structure are. 

 As is well known, " social " insects — bees, ants and termites — are 

 peculiar in the matter of sex. In all there are (1) drones (males) ; (2) 

 (pieens (fertile females) ; (3) workers (more or less infertile females) ; 

 whilst, in addition, the termites have (4) a form of the workers, modified 

 specially for fighting purposes and termed soldiers. 



It has been known, probably since the time of Virgil, that the 

 drones are developed parthenogenetically, i.e., from eggs not fertilised 

 by the sperm cells. The absence of sperm, then, seems to be the only 

 condition necessary for the development of the male form. An unfer- 

 tilised egg produces a larva, and no matter what nutritious or in- 

 nutritious food the larva may get in the course of its existence, it 

 changes to a pupa and produces a male in due course. It is not so with 

 the fertilised eggs. The stimulus of the sjierm is all-sufficient for the 

 production of females ; a fertilised egg nmst produce a female insect : 

 but Avhen the larva hatches, it is in the power of bees, ants or termites 

 to cause it to produce either a fully fertile female or a sterile female 

 by feeding it differently. For three days all the young female larvte 

 (i.e. all larva? from fertilised eggs) are fed alike. If, after that time, 

 a more nutritious and more plentiful diet be given, the bee, ant or 

 termite emerges a fully fertile female or queen. If, on the other hand, 

 the larva? are fed with a less plentiful supply of comparatively in- 

 nutritious food, they still produce females, but with smaller bodies 



