220 Mr Harrison, A preliminary account of the 
the oesophagus in front of the mid-gut. The Anoplura have 
neither crop nor proventriculus. In all three a pair of lateral 
caeca from the mid-gut project forward into the thorax, the 
malpighian tubes are four in number, and the arrangement and 
proportions of the hinder parts of the intestine are. identical. 
There are two: pairs of salivary glands, and, in the Ischnocera — 
and Anoplura, groups of specialised binucleate cells, richly tra- 
cheated, le about the ducts of these, at the base of the oesophagus. 
The respiratory system I have pr eviously shown to be practically 
identical in all three groups (1915); there being one thoracie and 
six abdominal pairs of stigmata, two main tracheal trunks, and a — 
system of four transverse commissures in connection with the 
four main nerve masses. In all Anoplura, and in some Mallo- — 
phaga of both sub-orders, the lateral trunks are connected by a 
posterior commissure. I have shown for Mallophaga, and Enderlein 
(1904) for Anoplura, that the abdominal stigmata, whatever their 
apparent position, are morphologically upon segments 3—8. 
In all three groups the heart is a round sac, situated dorsally 
in the eighth abdominal seginent, with two or three pairs of ostia 
dorsally in Mallophaga (Fulmek, 1905), three beg the number 
that I find in Pediculus. The heart is supported by three bundles 
of alary muscles on either side, in close relation with which are a 
group of half-a-dozen pericardial cells. The fat-body is similar in 
character and distribution, and in the larva is distributed in meta- 
meric pockets, each surrounding a little group of calcosphaerites. 
The nervous system in all three groups 1s identical, comprising 
a brain, sub-oesophageal ganglion, and three thoracic ganglia 
almost fused together. From the postero-lateral angles of the 
metathoracic ganglion a bundle of long fibres is given off to the 
viscera, ‘there bemg neither nerve cords nor ganglionic enlarge- 
ments in the abdomen. The nerve supply to eyes, tactile hairs, 
and other sensory organs, 1s identical. 
The reproductive system shows a still more remarkable simi- 
larity. In male Amblycera there are three pairs of testes, those 
of either side being evenly spaced upon the corresponding vas 
deferens. The latter open into a paired vesicula, showing more or 
less fusion, but in most cases completely fused, from which a 
common ejaculatory duct leads to an eversible sac in connection 
with the chitinous genitalia. The basal plate of the Amblycera is 
in most families of the sub-order only a chitinous rod, tapering 
anteriorly. In the Boopidae and some others, however, a true 
basal plate is developed. In Ischnocera and Anoplura the testes 
are four in number, the pair of either side being placed base to base, 
the corresponding vas deferens arising between the closely apposed 
bases. ‘The vesicula and ejaculatory duct have the same relations 
as in the Amblycera, but the vesicula of Pediculus is only fused at 
