REPORT 
ON THE 
CONTRIBUTIONS TO THE NATURAL HISTORY OF INSECTS, 
ARACHNIDA, CRUSTACEA, AND ENTOMOSTRACA, 
DURING THE YEAR 1842. 
BY 
DE. W. R EBICHSON. 
A Treatise, displaying profound research in the History of 
the Formation of Animals, “ IJber die riickschreitende Meta- 
morphose der Thiere,” by Hathke (Neuest. Schrift d. Naturf. 
Gesellsch. in Danzig, hi. Bd. 4 Hft. Beitrage zur Vergl. 
Anat. und Physiol, von Dr. H. Bathke, Danzig, 1842), is 
peculiarly interesting in the science of Entomology. 
The author calls that phenomenon, where, in the regular course of the 
development of the animals, particular forms of the organism shrink up, 
or even disappear, “ Retrograde metamorphosis” (riickschreitende me- 
tamorphose). This may either happen through dissolution (metamorph. 
retrogr. per dissolutionem), or through solution (met. ret. per solutionem). 
In the former case, the organs concerned become gradually melted away, 
while their elementary parts pass into the mass of the rest of the or- 
ganism ; in the second case, they are cast off with the cuticular coverings. 
This occurs with the hind legs of caterpillars, the legs of many parasite 
crabs, the eyes of several Entomostraca, as well as with some internal 
organs, as the branchiae of the larva of the Dragon Fly. The first case 
must always precede the second ; for, as the author remarks in regard to 
the eyes, where cornea, lens, and pigment are thrown off, the other parts 
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