ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
617 
the theory of mimicry. Although much support has been afforded to 
this theory since Bates propounded it in 1862, Col. Swinhoe states that 
no evidence is so complete and convincing as that supplied by the genus 
Hypolimncis. If we are right in believing that the results are deter- 
mined by the range and abundance of mimetic forms, it is clear that 
selection, rather than unguided variation, is the essential cause of the 
phenomena. 
Habits of Carrion-Eating Insects.* — Prof. Fr. Dahl calls his in- 
vestigation a study in Ethology or “ Biology in the narrower sense ” 
— a use of the term “ Biology ” which seems to us extremely undesirable. 
The point of his study is that it combines in natural conditions the two 
methods of experiment and statistics; and the author submits it not 
merely on its own account, but as an illustration of a method which 
deserves to be more frequently pursued. 
His experiment was simple enough. A dead sparrow, bereft of head 
and tail, and not too dry, was placed in a glass beaker and sunk in the 
soil, in different localities, at different seasons. Over the beaker was 
placed a glass fly-trap of bell-glass form with spirit at the base, and a 
simple contrivance by which carrion-insects might creep up from the 
carcass and land in the spirit. The contents were examined every week 
at least. 
As Megnin showed, the visitors vary according to the stage of 
decomposition, First, while the corpse is still without “ smell,” come 
Musca vomitoria , Cyrtoneura stabulans , Callipliora vomitoria (properly 
C. erythrocephala ) if the corpse is in a house, and others if it is in 
the open country. A second stage is characterised by Lucilia csesar 
(perhaps latifrons) and Sarcophaga carnaria , both from the open fields. 
Much later come species of Phora and Conicera and others. Besides 
insects, it may be that snails, mites, worms, and even a frog occur 
beside the corpse, but those who come for the carrion must be distin- 
guished from those who come for the sake of other visitors. 
Dahl gives a list of 54 species, noting their occurrence at different 
times of year, and their distribution in house, wood, marsh, field, dune, 
&c. He also discusses the factors which determine the occurrence of 
species at particular times. His observations show that there is more 
than temperature involved, and suggest that in the course of time 
periodicities at first directly environmental have now become organic. 
Some animals are always associated with special conditions ; others seem 
less sensitive and more independent ; for these two sets the terms 
“ stenotop ” and “eurytop”are suggested. The author confirms from 
his study of the carrion- visitors what is so familiar in regard to higher 
animals, that each organism has its distinct role in the economy of nature. 
He also notes the correlation between wide distribution of food and the 
wfide distribution of its consumers, and between irregular distribution 
of food and the development of sensory and locomotor organs on the 
part of the consumers. 
Changes of the Intestinal Epithelium in the Metamorphosis of 
Mealworm. f — Herr C. Rengel has studied these changes in Tenebrio 
* SB. K. Akad. Preuss., 1896, pp. 17-30 (2 figs.). 
t Zeitsclir. f. wiss. Zoo]., lxii. (1896) pp. 1-60 (1 pi.). 
