DR. F. LEUTHNER ON THE ODONTOLABINI. 405 
tooth gradually disappears. Finally, nothing but the front tooth remains at the tip, 
which becomes considerably curved inwards, like a hook (no. 1). 
Here too, as in 0. alces, we pass without a break (but from an amphiodont form which 
most resembles the female) to the terminal form by gradual lengthening and simplifica- 
tion of the mandibles. But no one will ever be able to prove the opposite, as the small 
forms of mandible are always more complicated in structure. A more complicated form 
can never arise from a more simple form by arrest of development, 
The results at which we arrived through the study of O. alces are thus confirmed, 
and we are consequently obliged to regard the mesodont, amphiodont, and priodont 
forms as stages of the development of the mandibles, and as antiquated forms which 
still reappear from causes which we do not understand, The smallest male is so similar 
to the female that one of the most eminent entomologists, who first described 
Heterochthes brachypterus, an allied species, mistook one of these small males for a 
female, and described and figured it as such !. 
But if, instead of studying Coleoptera, in which the metamorphosis is complete, and 
each imago can only represent a single form, so that its history can only be studied 
Head and buccal apparatus of Anostostoma australasie. 
No. 1, full-grown ¢; no, 2, ditto, side view; no. 3, full-grown 9; no, 4, early larval stage of ¢ 
with mandibles like those of °. 
by a phylogenetic method and by series, we were dealing with insects with incomplete 
metamorphoses, in which we might be able to trace the gradual development of the 
* Trans. Ent. Soc. Lond. (3) ii. pl. x. fig. 6. 
