TURBELLARIA. 
531 
median line of the back, surrounded by a special muscular sheath, 
within which it glides in a highly organized corpuscular fluid, passing in 
front between the commissures of the ganglia, while the digestive tract 
is placed inferiorly. Sexes separate in the majority, oviparous or ovo- 
viviparous ; sexual organs in the form of sacs placed between the mus- 
cular wall of the body and the digestive canal.” 
A. Enopla. Proboscis furnished with stylets. Blood-vessels more dif- 
ferentiated than in the Anopla, The young, as far as is known, do not 
undergo any noteworthy metamorphosis during their growth. 
I. AmphiporidcB. Nerve-ganglia rather rounded, somewhat double ; 
lateral nerve-trunks placed within the proper muscular walls of the 
body; mouth opening on the ventral surface of the snout in front of 
the commissures of the ganglia. 
a. Amphiporince, Proboscis proportionally large. These animals as a 
whole have comparatively short and thick bodies, 2 muscular layers in 
the body wall, an external circular and an internal longitudinal ; the pro- 
boscis is composed of 3 divisions, the anterior having 7 coats, the middle 
bearing the stylets, the posterior forming a long sac with 2 muscular 
coats ; 3 great longitudinal vascular trunks, 2 lateral and 1 median, be- 
sides a cephalic arch ; the cephalic sacs or glands are accompanied by 
long tubes or ducts. 
1. Amphiphorus^ Ehrbg. Eyes more or less numerous and large, but 
never arranged in a square. Body rather short, sometimes flattened ; A. 
lactifloreus, Johnst., p. 156, pi. i. figs. 1 & 2; A. pulcher^ J., p. 158, pi. i. 
fig. 3, & xiv. fig. 11 ; spectahilis, Qu., p. 160, pi. iii. figs. 2, 7 & 8; has- 
tatus, p. 162, pi. viii. fig. 2, and hi-oculatus^ p. 163, pi. viii. fig. 3,spp- nn. 
(Shetland). 
2. Tetrastemma, Ehr. Eyes 4, arranged so as to indicate a square or 
oblong. T. melanocephala, J., p. 165, pi. ii. fig. 1 ; robertiana^ sp. n., 
p. 166, pi. iii. fig. 1 ; Candida^ Mull., p. 167, pi. ii. figs. 2 & 3 ; vermicula^ 
Qu., p. 169, pi. iii. fig. 3; Jiavida, Ehr., p. 170, pi. iv. fig. 1 ; dorsalis^ 
Abgd., p. 172, pi. i. fig. 4, & iii. fig. 4. 
3. Prosorrhochmus, Kef. Eyes 4, not forming a square ; snout dimpled 
and furnished with a transverse superior lobe ; ovo-viviparous. C. cla- 
paredii^ Kef., p. 174, pi. ii. fig. 4. 
b. Nemertinea. Proboscis proportionally small, the anterior region 
especially being shortened, so as to cause the stylet to approach the 
ganglia. Body more or less elongated ; in other respects with the cha- 
racters of the Amphiporinw. 
4. N enter tes, G\xy. N. gracilis, J., p. 176, pi. ii. fig. 5; neesi, Orst., 
p. 178, pi. iii. fig. 6, and pi. vii. fig. 6 ; carcinophila, K611., p. 180, pi. i. 
fig. 5. 
B. Anopla. Proboscis without stylets. Nerve trunks generally 
placed between the muscular layers of the body wall. The mouth 
opens on the ventral surface behind the commissures of the ganglia. 
The blood-vessels are somewhat less differentiated than in the Enopla, 
The young in the most conspicuous families undergo a remarkable meta- 
morphosis. 
II. Lineidce. Ganglia more or less elongated ; muscular layers of the 
