868 PROFESSOR E, RAY LANKESTER. 
preoral region. On this account the two pairs of przoral 
appendages have been looked upon as being aboriginally 
appendages of the region in front of the mouth and in 
various other Arthropoda (e.g. the Arachnida and Limulus) 
the attempt has again and again been made to determine 
whether the first pair of appendages which are present ina 
given case are to be considered homologous with one of the 
preoral pairs of appendages of the Crustacea by an ex- 
amination of the nerve-supply—it being held that if an 
appendage received its nerves from the preoral ganglion it 
would necessarily be the homologne of one of the similarly 
innervated preeoral appendages of the Crustacea. 
Anton Dohrn, for example, in discussing the affinities of 
Limulus, says: ‘‘ Bei allen Krustern empfangen namlich die 
beiden vorderen Extremitatenpaare ihre Nerven aus dem 
oberen Schlundganglion.” And so firmly fixed is this con- 
ception with regard to the nerve supply of the two pairs of 
preoral appendages in Crustacea, that Dohrn has made it 
a subject of special remark that in certain Nauplius larve 
the first pair only (the antenuules) receive their nerves from 
the preoral ganglion, whilst the second receive their nerves 
from the lateral cords, which pass posteriorly to form the 
ventral ganglionated cord. 
Claus, who described this difference in the mode of nerve 
supply of the two preoral appendages of larval Phyllopoda, 
is led by it to a remarkable conclusion as to the nature of 
the two pairs of przoral appendages of Crustacea. He holds 
(‘ Grundzuge der Zoologie,’ 3rd edition, p. 518) that because 
in these Nauplii the first pair of antennz are supplied by 
the cerebral or preoral ganglion they are the equivalents of 
the antenne or tactile appendages of the cephalic lobe of 
Cheetopoda (Annelides) ; whilst the second pair of Nauplius 
appendages, or second pair of antenne, are to be regarded 
as equivalents of postoral segmental appendages of Cheto- 
poda, because they receive their nerves from the lateral 
cords and not from the preoral ganglion. 
I have long been of the opinion which Prof. Claus appears 
to hold, that the appendages of the Arthropoda are homo- 
logous (or, to use a more distinctive term, ‘‘ homogenous ”’) 
with the appendages of the Chetopoda, and on this account 
I consider it a proper step in classification to associate the 
Cheetopoda with the Arthropoda and Rotifera in one large 
phylum, the Appendiculata (see “ Notes on Embryology 
and Classification,’ this Journal, 1876, and Preface to the 
English translation of Gegenbaur’s ‘ Elements of Compara- 
tive Anatomy ’). 
