50 
THE MUSEUM. 
Planarians, distinguished as the head, is commonly furnished with a pair of eyes, 
though some genera possess a greater number. 
Of our fresh water Planarians, the most common is the Planaria metadata. It 
ranges from two to seven lines in length; ordinarily, in motion, about half an inch by 
a line in width. The upper convex surface is variably brown to black, uniform or 
with indistinct scattered spots of a lighter hue. The under surface is of uniform 
lighter hue and more translucent. The color is more or less modified by the stomach 
and its contents shining through, variably distinct and usually brown, but sometimes 
with a greenish or reddish tint. At rest the animal is shorter and wider and appears 
as an oval or ovoid disk. In motion, when the body is most extended, it is lanceolate, 
acute behind, and with the head triangular and varying to diamond shape, according 
to the degree of expansion. The front and lateral angles of the head are variably prom¬ 
inent, obtuse or acute, and are frequently erected in the movements of the animal, as is 
also the case with the entire head. The eyes, at the base of the head, near together, appear 
as a pair of black, cup-like spots at the bottom of an oval, colorless space. The mouth is 
behind the centre of the ventral surface; the proboscis is a simple cylindrical tube ; 
and the stomach presents the usual dendritic arrangement. This Planaria is found 
in almost every brook, pond, creek and river. It appears to be nocturnal, and in the 
daytime lies concealed on the under side of stones, often in considerable numbers 
together, associated with a variety of other aquatic animals. In motion in a dish of 
water it glides along the bottom, like a snail, often ascending at the sides and turning 
upside down swims on the surface, likewise in the manner of fresh-water snails, like 
Physa and Limnaea. It is abundant under stones in the Delaware and Schuylkill 
rivers, in association with little leeches of the genus Clepsine, the brown Hydra, etc. 
Another Planarian, less common than the former, though also frequent in similar 
positions, is the Procotyla fluviatilis . It is milk-white, though occasionally marked 
by the brownish color of the dendritic stomach. It has nearly the size, shape and 
structure of Planaria maculata. The head is rather abruptly truncated, with 
the lateral angles variably prominent and rounded. The front is provided with a 
median cup-shaped sucker, capable of protrusion and expansion and of retraction. 
The eyes usually consist of a single pair at the centre of the head, but the number is 
not unfrequently variable. I have observed from one to four pairs, forming two lon¬ 
gitudinal rows. Occasionally the number varies on the two sides of the head. In 
one instance I saw an individual with one eye on the right and three eyes on the left, 
and in another instance two eyes on one side and five eyes on the other. Each eye is 
composed of a black cup enclosing a transparent vitreous body, and distinctly con¬ 
nected behind with a nerve. In some individuals I have observed the posterior 
branches of the stomach variously anastomose with each other. In movement the 
animal uses its frontal sucker to adhere to surfaces, just as the leech does by its caudal 
sucker. This species I have found abundantly in the Delaware and Schuylkill rivers, 
and especially in the ditches of the meadows communicating with these, below the 
city of Philadelphia. It is often found attached to the submerged stems of plants; 
