-APPENDAGES AND NERVOUSSYSTEM OF APUS CANCRIFORMIS. 869 
At the same time I have not been led to conclude, as 
Prof. Claus does, that only one pair of the Crustacean 
antennz are to be regarded as primarily postoral in posi- 
tion, and as representing the appendages of two originally 
postoral somites, but I think it probable that doth antenne 
are in this case, and that in the Crustacean there is no 
representative of the “ antennz ” or tactile processes of the 
cephalic lobe of Chzetopoda. Whilst this appears to me 
probable in regard to the Crustacea, it yet seems to 
me very possible that the antenne of Peripatus and of 
Hexapod and Myriapod insects may represent true pro- 
cesses of the cephalic lobe or prostomium, as seen in 
Cheetopoda. 
In 1873, in the ‘ Annals and Mag. of Natural History’ 
for May, p. 336, 1 said: “ Much more likely, it seems, is 
the explanation that the oral aperture shifts position, and 
that the ophthalmic segment alone in Arthropoda represents 
the prostomium, the antennary and antennular segments 
being aboriginally metastomial, and only prostomial by later 
adaptational shifting of the oral aperture.’ I was led to 
take this view by a consideration of the relations of the 
mouth to the appendages in Nauplius, and by the facts of 
the constitution of the head and its appendages in the 
Cheetopoda. 
Prof. Claus’ removal of the second pair of antenne from 
the prestomial to the metastomial region is based on a solid 
embryological fact as to the innervation of that appendage 
in the Nauplius, but it appears to me that the facts ascer- 
tained by Zaddach and Grube as to the structure of the 
nervous system and the supply of the appendages in certain 
adult Phyllopods—facts which were unknown to me in 
1873—entirely confirm and establish on a firm basis the 
view that, in the Crustacea at least, the two preoral pairs of 
appendages are primitively postoral, and are neither of 
them related to the primitive prostomium or cephalic lobe, 
viz. the region innervated by the primitive cephalic ganglion, 
which ganglion I will venture, for want of a better name, to 
call the ‘ archi-cerebrum ’ of the Appendiculata. 
The condition of things described and figured by Zaddach 
in Apus cancriformis is represented in the woodcut, fig. 2. 
The nerves to both pairs of antenne are seen to arise, not 
from the quadrangular archi-cerebrum, but from the lateral 
cords at some distance from it, which are continued poste- 
riorly to form the so-called ‘ ventral’ nerve ganglion chain. 
A similar but less considerable separation of the nerves to 
the first pair of antenue from the cerebral ganglion is de- 
