SPECIES OF PLANARIAN WORM. 37 
“inverted club-shaped eyes.” The eyes of Rh. Howesi belong to 
the other or “retina” type. It consists simply of a cup-shaped 
organ internally coated with small pigment-cells and surrounded 
by a retina, so that the latter is placed facing the light. The 
open part of the cup is covered by a non-pigmented layer of 
cells—a kind of cornea. The latter has a thickness of 0°012 
millim.; while the whole eye is 0°16 millim. long, and at its 
widest part 0°L08 millim. broad. The interior of the eye is 
partly filled with a peculiar cellular substance, whose true nature 
could not be ascertained from any of the sections available. I 
had no means of comparing the sections with longitudinal ones, 
and must presume that this structure is similar to that figured 
by Prof. von Graff (2. pl. 50. fig. 1). He explains (p. 144) that 
it is composed of a bundle of elongated columns, one end of 
which converges towards the centre of the eye, whilst the others 
are connected with the retina-cells by means of fine prolonga- 
tions which pass outward between the pigment-cells. 
Connective-tissue (Pl. 6. fig. 3, ¢.¢.) binds together the various 
organs and structures lying within the epidermis and maintains 
them in position. It consists of a mass of fibres containing nuclei, 
and bearing also the generaliy small pigment granules which pro- 
duce the black colour of the skin. The digestive organs do not 
extend to the most anterior part of the body, and are therefore 
not visible in the section (PI. 6. fig. 3), but a little farther back 
we find a considerable part of the transverse sections occupied 
by the alimentary canal (text-fig. 1, a). 
All Land-planarians and also the marine and freshwater 
Triclads agree in the possession of an alimentary canal consisting 
of three main branches and a muscular pharynx. One of the 
main branches runs anteriorly, the two others (text-fig. 1, 
r.al., l.al.) occupy the posterior portion of the body, and they all 
join in a common opening in front of the pharyngeal sac. 
I have already mentioned that the pharynx had become pro- 
truded through the mouth during the violent contractions when 
the worm was preserved. The mouth, as stated, is situated 40 
millim. behind the anterior end of the body, and is indicated by a 
minute transverse slit scarcely visible in the living animal. The 
large pharynx, as seen in text-fig. 1 (ph), is somewhat cylindrical: 
and conically pointed at the free end. ‘Che transverse section 
figured is close to the external pharyngeal opening, and shows 
peculiar folding of the pharyngeal epithelium. Cilia were 
