1897.] Zoology. 445 
The occurrence in crustacea of an antenna-like organ in the place of 
an eye was noted as early as 1864 by Milne-Edwards’ in the lobster, 
Palinurus penicillatus, and later (1894) by Hofer’ in Astacus. To ask 
what bearing these cases and the results of Herbst’s experiments have 
upon the general question of arthopod segmentation is but to repeat the 
query made by Milne-Edwards. He thought that he had found new 
evidence of the truth of Savigny’s law. Later, writers have not gener- 
ally considered the eye or optic stalk as the homalogue of a segmental 
appendage, nor have they considered the protecerebral lobe, from which 
the eye is innervated, as evidence of a segment. It may bea hasty 
conclusion, but the cases of an antenna-like structure certainly seem 
to indicate that Milne-Edwards was right, and that one may in the 
future be obliged to consider the arthopod head as having one more 
segment in it. than we have till now supposed it to have. Further 
experimentation is necessary to show what internal structures are 
regenerated, for Herbst seems to have made no sections whatever 
of the structures that he describes. One would like to know to just what 
extent the muscles are developed, and what happens to the stump of the 
optic nerve. Experiments should also. be made to determine what, if 
8 Hofer. Ein Krebs mit einer Extremitit statt eines Stielauges. Verh. d. 
Deutsch. Zool. Gesel., 1894. 
? A, Milne-Edwards. Comp. Rend. Acad. Sci.. Paris (1864) LIX, pp. 710-12. 
è 
