A Description of three Acoela from the Gulf of Naples. 
297 
Äphanostoma pulchella belongs to the later type. It is highly developed 
and typical in shape (pi. 10, fig. 1). The lobes extend posteriorly to 
the level of the mouth, and closely surround the brain and statocyst. 
This gland and the mucous glands of the integument as well as the glan- 
dulär tissue of the reproductive organs, stain a briUiant blue in Dela- 
field's Haematoyxlin. 
The mouth, which is near the anterior end of the body (pi. 10, fig. 1 
and text-fig. 4) opens on the ventral surface, posterior to the statocyst. 
The pharynx consists of a short circular tube with thick muscular walls. 
In my preparations I have not seen the "superimposed tubes" which 
Pereyaslawzewa described. 
The nervous system is composed of a small mass of cells surrounding 
the statocyst. There are no eyes present. No nerve fibres have been 
observed. 
The parenchyma is loosely aranged with largo spaces between the 
cells giving it a vacuolated appearance (figs. 3 and 4). At the extreme 
posterior end the cells are largo (pi. 10, fig. 1, and text-fig. 4), resembling 
those in the same region of ÄpJianostoma diversicolor. 
The reproductive products ripen in Äphanostoma pulchella at dif- 
ferent periods, the male organs maturing first, and the female later. For 
this reason when the eggs are mature the testes and vasa deferentia are 
small and inconspicuous. When fuUy developed the folhcular testes 
extend forward on each side as far as the frontal gland (fig. 1, t). Their 
Position is dorsal and lateral to the ovaries. The paired vasa deferentia 
are coiled in loose loops on each side of the copulatory organ. The ripe 
spermatozoa are frequently observed lying in bunches (fig. 2, sp) in the 
parenchyma. They have largo rounded heads, and thread-like tails 
just as Uljanin described them in Nadina pulchella. The penis, or copu- 
latory organ, is the largest and most conspicuous organ in the body (pi. 10, 
fig. 1, text-fig. 2 and 4). It opens to the exterior near the beginning of 
the posterior half. In the living worm, when slightly cempressed dorso- 
ventrally, it resembles a muscular ball with a hole in the center (pi. 10, 
fig. 1, p). In transverse and sagittal sections (figs. 2 and 4, p) it is shaped 
like a stout flask, whose walls are composed of many layers of muscle. 
These muscles extend into the neck of the flask, and out to the surface. 
On each side of the orifice the muscular walls are surrounded by masses 
of glandulär tissue. Whether or not the penis is evertible I have been 
unable to ascertain. 
The antrum femininum hes immediately in front of the penis so dose 
to the male genital opening that it might easily be overlooked. It leads 
