546 Proceedings of the Royal Society 
inferiority. Sexes separate in the majority; oviparous or ovo- 
viviparous. 
The Order may most naturally be separated into two great Sub- 
Orders, distinguished from each other by the presence or absence 
of stylets in the proboscis, the former being called after Max 
Schultze, (but with amended characters), Enopla , and the latter 
Anopla. 
The Sub-Order Enopla is characterised further by the rounded 
and somewhat double nature of the nerve-ganglion on each side, and 
by the fact that the lateral nerve-cords are placed within the proper 
muscular walls of the body. The mouth, moreover, opens on the 
ventral surface of the snout in front of the commissures of the 
ganglia. The blood-vessels are more differentiated than in the 
Anopla. The young, so far as known, do not undergo any note- 
worthy metamorphosis. 
In the Enopla there exists one great group, and a subordinate 
one, which, however, retains so many of the characters of the 
former, that it has not been considered advisable to separate it into 
a distinct Family, but both have been placed under the Family 
Ommatopleidce. The animals forming this Family have two mus- 
cular layers in the body-wall, an external circular and an internal 
longitudinal ; the proboscis is composed of three divisions, anterior, 
middle, and posterior, — the former having in the typical forms seven 
coats, viz., external elastic, external longitudinal (muscular), re- 
ticulated or beaded layer, inner longitudinal, circular, basement 
layer, glandular layer. The middle region bears the stylets, and 
the posterior forms a long sac, with two muscular coats — external 
circular and internal longitudinal. There are three great longi- 
tudinal vascular trunks, two lateral and one median. The cephalic 
pits and glands are accompanied by long tubes or ducts. The sub- 
division of the Family referred to may be made by separating those 
(A) with comparatively short and thick bodies, and proportionally 
large proboscides ; and (B) those having more or less elongated 
bodies, and proportionally short proboscides. 
The Sub-Order Anopla, again, is further distinguished by having 
the nerve-cords placed between the muscular layers of the body- 
wall. The mouth opens on the ventral surface behind the commis- 
sures of the ganglia. The blood-vessels are somewhat less differ- 
