( Ixix ) 



masses, that the mass of food stored is not subject to much 

 variation. As just stated, the size of the female of a species 

 is not very variable, except as a rare occurrence, and this 

 rare variation appears always to consist in great diminution 

 of size, so that the individuals affected are comparatively 

 dwarfs. In looking through a large number of such indi- 

 viduals I find that these dwarfs appear, as far as one can 

 judge, to be about half the weight of normal examples, and 

 one is led to suppose that they are produced from two eggs 

 having been laid in a single cell of the bee, a fact which is 

 known to take place in some instances. 



The variation in the males is less regular, dwarfs occur as 

 in the females, and specimens both notably above or below 

 the mean size are frequently observed, but amongst these 

 there stand out conspicuously the giant individuals, as a 

 phenomenon quite distinct from anything observed amongst 

 the females. We may note that these huge males frequently 

 approach closely in bulk that of the average-sized female, 

 but it is a matter of great doubt how they are produced. 

 It can hardly be a question of a simple surplus over the 

 usual amount of food, since gigantic females do not occur, 

 unless we suppose that the surplus nourishment goes to form 

 superior size in the case of one sex and some other develop- 

 ment in the other. This is not inconceivable, since we know 

 that the drain on the strength of Andrena by the parasite 

 Stylops is such as to cause almost invariably, if not always,* 

 a degeneration of the ovaries in the females, these organs 

 requiring much nutriment, while in the males, according to 

 my own observations, practically confirmed by those of 

 Geoffrey Smith and A. H. Hamm, little or no degeneration 

 of the comparatively small genital glands is produced. Con- 

 sequently a surplus of food might in the case of the females 

 be used up in the nutriment or growth of the important 

 ovaries, while this might be used for a general increase in size 

 in the males. 



We know, from observations on cells superimposed one on 

 the other and with only one exit, that the eggs which will 

 produce males and those which will produce females are not 



* According tu the observations of Geoffrey Smith and A. II. Hamm. 



