284 NATURAL SCIENCE. April. 



Let us now turn to the alleged progressive development of the 

 workers, and consider whether the argument of the selectionist is any 

 stronger in regard to these. The first instance cited by Weismann 

 is the great increase in the brain. The females, never having had 

 any brains to speak of themselves, are alleged to have acquired, as 

 the result of selection, the property of generating workers with large 

 brains. In the first place, I would point out that I know of no 

 careful comparison between the brains of a newly-emerged worker 

 ant and a newly-emerged queen. It is in accordance with well- 

 established facts to conclude that after emergence the brain of the 

 worker ant grows larger, while that of the perfect female diminishes, 

 simply as a result of use and disuse in the individual. Spencer 

 maintains that apparent gains on the part of the worker are really 

 due to the persistence of organs and characters which have diminished 

 in the fertile insects. I am not prepared to say that these two 

 principles fully explain all the apparent plus modification exhibited by 

 sterile workers ; but I do maintain that no sufficient evidence has yet 

 been brought forward to show that constitutional characters are 

 present in the workers which have been evolved in them alone, and 

 are neither due to the action of conditions on the individual develop- 

 ment nor to inheritance from the original ancestors. 



Weismann lays great emphasis on the enlarged heads and jaws in 

 the so-called soldier caste in certain species, such as Pheidole mega- 

 cephala and Colohopsis tvuncata. But it must be pointed out that the 

 very fact that this character distinguishes a special caste of workers 

 is difficult to reconcile with the explanation upheld by Weismann. 

 For, as Lubbock says, the question arises whether those different kinds 

 of workers are produced from different eggs. Lubbock (3) speaks 

 from special and original knowledge of these insects, and he is dis- 

 posed to concur with Westwood, that the inhabitants of the nest have 

 the instinct so to modify the circumstances producing this state of 

 imperfection, that some neuters shall exhibit characters at variance 

 with those of the common kind. Considering the established fact 

 concerning bees, it is by no means an extravagant suggestion that 

 where there are two or even more castes of workers, the eggs are all 

 essentially similar, and simply developed under definite differences of 

 conditions. If this is the case, and the presumption is that it is, then 

 there is no evolution of the castes in the sense of the modification of 

 the characters predetermined in the eggs. It must be remembered 

 that in all these polymorphic social insects the larvae may be said to 

 be artificially developed. The conditions in which the larvae live are 

 contrived by the full-grown workers, and are kept wonderfully constant. 

 We cannot say, as even Weismann would admit, that the small feet 

 of Chinese ladies are due to phyletic metamorphosis or to Natural 

 Selection. Their growth is moulded and checked by the unyielding 

 influence of material bonds, and we have good reason to suppose that 

 equally rigid external conditions mould the developing larvae of ants, 



