224 The American Naturalist. [March, 
xi, p. 2) that “the immediate ancestor of the Arachnida was 
constructed somewhat as follows: The body was composed of 
eighteen somites, the anterior of which were provided with 
large appendages set apart for locomotion and the prehension 
and mastication of food ; the terga of this cephalothoracic re- 
gion were fused to form a single shield or carapace, supporting 
a submedian and a cluster of lateral eyes at each side, and the 
ventral surface of the carapace [? cephalothorax], at least in 
its posterior half, was protected by a sternal plate. Each of 
the succeeding six somites bore a pair of small ventral append- 
ages, and the generative aperture opened upon the sternal area 
of the first of these somites. The posterior six somites had lost 
their appendages, were probably narrower than the rest, and 
constituted a limbless caudal portion of the body, the last of 
them being furnished with a single plate, articulated above 
the anal aperature.” This should be compared with one of 
the Eurypterida. 
Sus-Poytum I]—Insectra SIVE ANTENNATA. 
Arthropods with differentiated head consisting of proceph- 
alic lobes and four (five’) somites ; head with somites anchy- 
losed and provided with four pairs of appendages modified for 
sensation or for feeding ; respiration by means of trache® (mod- 
ified glands) opening to the exterior on the sides of the body — 
in the post-cephalic region. Nephridia absent, except as genr 
tal ducts, which open near the posterior extremity of the body: 
Ectodermal Malpighian tubes present. Spermatozoa motile. 
So far as I am aware, the dissolution of the old group Myr 
apoda and the union of the Chilopoda with the Hexapod ner 
first proposed by Pocock (’87). At about the same er 
taught the same view to my classes, and later (’88) ae ft) 
the same. Subsequently both Pocock (’93) and I (93, r , S it 
repeated our views within a month of each other‘ pie 
seems to me, is fully justified. The affinities of the Chile 
to the Hexapods are most close, while those of Chilopoda 
5 See p. 125. 
sOneof our best students of the Myriapoda, the late C. H. Bollman; m 
views and they appear in the posthumous collection of his papers ('93). 
