LIMULUS AN ARACHNID, 631 
together, on the one hand, are compared with Scorpio, on the 
other. 
Claus (14), as late as 1881, adopts exactly Dohrn’s view 
of the systematic position of Limulus. He accepts the 
group Gigantostraka (including Merostomata and Xipho- 
sura), and places it as a division of the class Crustacea, in 
opposition to the Eucrustacea, consisting of the great sub- 
classes Entomostraca and Malacostraca. Of the relationships 
of the Gigantostraka to Arachnida, Claus says nothing. 
Owen (7), in his monograph on the King Crab, discusses 
Dohrn’s views and brings to the question a large mass of 
anatomical and paleontological fact. His conclusion that 
Limulus exemplifies “ that lower condition of the Crustacea 
which has been expressed by the term Entomostraca,” is 
vitiated by the fact that although one of the first to recog- 
nise that the “‘ chilaria”’ are sternal elements and not appen- 
dages, he yet seeks for the representatives of missing body 
segments in the postanal spine, and, above all, it is falsified 
by his adhesion to the opinion of Van der Hoeven, that 
two pairs of appendages are innervated from the cerebral 
ganglion. That no appendages are so innervated is now 
demonstrated by the dissections of A. Milne-Edwards which 
I have confirmed ~ Accordingly, Professor Owen would now 
probably be amongst the first to admit the affinities of 
Limulus with the Arachnida, since he observes: ‘ If it 
were a fact that in Limulus only the foremost pair of limbs 
was innervated from the supercesophageal ganglion, the rest 
deriving their nerves from the abdominal ganglionic chain, 
the advocate for its elimination from the Crustaceous class 
would have an argument of weight for the affinity of Limulus 
and its extinct allies with the Scorpion and the Spider.” 
Huxley (16), who has at various times approached the 
question of the affinities of Limulus, holds that it has 
relationships, on the one hand, through the Eurypterina to 
the Copepod Crustaceans, and on the other hand, to the 
Phyllopoda through the Trilobites, and again independently 
to the Scorpion. At the same time he definitely places it 
in the class Crustacea in the order Merostomata, together 
with Eurypterina and the Trilobites. Presumably this 
implies that Limulus is a nearly related representative of an 
ancestral form which gave rise to the Copepods as one 
branch, to the Trilobites and Phyllopoda as another, and to 
the Arachnida as a third. 
Without discussing for the moment the possibility of any 
close connection between the Phyllopoda and Trilobites, | 
may remark that the connection of Limulus and the Eury- 
