144 
ME. H. N. MOSELEY ON THE ANATOMY AND 
says, “ Les deux lobes de cette espece de cerveau sont composes dune substance entiere- 
ment diaphane et homogene.” Keferstein is the only investigator, so far as I am 
aware, who has made sections of these organs in Planarians and recognized their true 
structure, whilst M‘Intosii ( loc . cit. pi. vii. fig. 2) has figured nerve-cells from the ganglia 
of Nemertines. Keferstein gives a figure of a section of the ganglia of Leptoplana 
tremellaris , but the wonderful complexity of the nervous structures is not so minutely 
treated as in the present drawings. 
Special Sense-organs. — The only special sense-organs observed in Bipalium were the 
eyes and the peculiar organs on the anterior margin of the head. In Bhynchodemus a 
single pair of eyes was all that could be found. 
The eye-spots which appear when Bipalium is viewed with a hand-lens as black 
specks, are thickly set all over the upper surface of the flat semilunar head, except 
along its median line, a small space (broader anteriorly) on each side of this, and 
along a narrow band bordering the actual anterior margin of the head. The eyes 
are especially densely packed at the tips of the corona of the head, and are thickly 
set along all its margin, except in the region of the band of special sense-papillse. 
Besides this, eyes are present sparingly scattered over the entire length of the body to 
the very tail. It has hitherto been supposed by all writers on the subject that the eyes 
were confined to the anterior extremity in Bipalium ; but the spots are constantly being 
met with in sections in the region of the mouth and generative organs. Claparede, 
examining the eye-spots of B. Phoebe , could not make certain whether they were sense- 
organs at all. His specimens probably were not in sufficiently good preservation. In 
B. Diana , B. Ceres , and B. Proserpina the eye-spots are usually of the form shown in 
Plate XV. figs. 6 & 7, though they are often less elongated and indeed nearly spherical. 
They consist of a simple sac or cell, the anterior portion of which, or that turned to 
the light, is transparent and lens-like, whilst the posterior and larger portion of the 
sac is darkened and rendered opaque by the presence of brown pigment-granules 
imbedded thickly in its wall. An unpigmented dot, often present in the posterior part 
of the eye-spots and represented in Plate XV. fig. 6, seems to show that these eye-spots 
are to be regarded as modifications of single nucleated cells. 
In the interior of the eye-spot, when seen in section, is to be observed, under favour- 
able circumstances in deeply stained sections, a lens-like body (Plate X. fig. 7) ; but this 
body is very little differentiated from the general cell-contents, and is hard to see. 
Between the lens-like body and the interior of the pigmented back of the eye-spot is a 
highly refracting substance. No nervous structures were observed in connexion with 
the eye-spots. The eyes are arranged beneath the external circular muscular coat of 
the body, and in the intervals between the external longitudinal muscular bands (Plate 
XV. fig. 9). The light which reaches them must penetrate the external circular muscles 
first ; but these are not thick in the regions where the eyes are most numerous. 
Bhynchodemus possesses only a single pair of eyes, but these are very much larger 
than those of Bipalium ; they are elongate, and somewhat like those of the leech in 
