442 
PAUL PELSENEER. 
We observe, then, that from the Crustacea with the most 
primitive nervous system to the most superior forms there 
are a great many transitions (Apus, Branchipus, Daphnia, 
Phronima, Astacus) between the condition in which the 
nerves of the two pairs of antennae come out of the cord, and 
the condition in which these nerves come out of the brain. 
Since then a histological examination shows in Apus, 
which among the actual Crustacea has the most primitive 
nervous system, that the brain is a syncerebrum, and since 
among superior Crustacea the anatomy of the nervous system 
shows that the brain is at least as complex as in Apus, it 
seems very probable that among living Crustacea there are not 
any with an archicerebrum. 
The classification of the brains of Crustacea established by 
Packard 1 has no grounds whatever. 
1 ‘ American Naturalist,’ 1882. 
