EMBR YOLOG Y 261 



parents to any conceivable extent. Differences in the 

 larva might, also, become correlated with successive stages 

 of its development; so that the larva, in the first stage, 

 might come to differ greatly from the larva in the second 

 stage, as is the case with man}' animals. The adult 

 might also become fitted for sites or habits, in which 

 organs of locomotion or of the senses, etc., would be 

 useless; and in this case the metamorphoses would 

 be retrograde. 



From the remarks just made we can see how by 

 changes of structure in the young, in conformity with 

 changed habits of life, together with inheritance at corre- 

 sponding ages, animals might come to pass through stages 

 of development perfectly distinct from the primordial 

 condition of their adult progenitors. Most of our best 

 authorities are now convinced that the various larval and 

 pupal stages of insects have thus been acquired through 

 adaptation, and not through inheritance from some ancient 

 form. The curious case of Sitaris — a beetle which passes 

 through certain unusual stages of development — will illus- 

 trate how this might occur. The first larval form is 

 described by M. Fabre as an active, minute insect, fur- 

 nished with six legs, two long antennae, and four eyes. 

 These larvae are hatched in the nests of bees; and when 

 the male-bees emerge from their burrows, in the spring, 

 which they do before the females, the larvae spring on 

 them, and afterward crawl on to the females while 

 paired with the males. As soon as the female bee de- 

 posits her eggs on the surface of the honey stored in 

 the cells, the larvae of the Sitaris leap on the eggs 

 and devour them. Afterward they undergo a complete 

 change; their eyes disappear; their legs and antennae be- 



