TAA 
FULLY DEVELOPED EEL. 
cies. The two species are so similar in nearly 
every respect that they would naturally be sup- 
posed to have the same breeding habits. 
The distribution of the eel on both sides of 
the Atlantic has been carefully studied by Dr. 
Schmidt. 
side of the Atlantic, and these are apparently 
Only one species is known on each 
kept apart by the greater depths of the middle 
Atlantic. 
continents penetrated by the eels, but they are 
also found in the fresh water streams of the 
Not only are the inland waters of both 
oceanic islands, such as the Bermudas and 
Azores, from the tropics northward to Iceland, 
even in islands where no other fresh-water fishes 
exist. The European species occurs from North 
Cape southward to the coast of Morocco in Af- 
rica and throughout the tributaries of the Baltic 
It is not found in the 
Our Amer- 
and Mediterranean Seas. 
Black Sea nor its tributary streams. 
ican species is distributed from Labrador and 
the southern end of Greenland to Guiana, but is 
rare along the southern coast of the Caribbean 
Sea. 
It will be noticed that the eel reverses the 
breeding migration of the salmon, shad and other 
well-known fishes that breed in fresh and shal- 
low waters, while their young return to the ocean 
for their growth period. Their peculiar habits 
make it impossible to propagate them by artifi- 
cial methods or to establish them in other re- 
gions of the world where the special conditions 
The 
young eels can be readily transported and will 
of the breeding grounds do not exist. 
grow well in fresh water anywhere, but attempts 
to establish the American eel on the Pacific coast, 
have met with no results beyond the growth of 
the individuals transported, and the same has 
been true of the attempt to plant the European 
eel in the Danube and other tributaries of the 
Black Sea. RACLO: 
ZOOLOGICAL SOCIETY BULLETIN. 
SKATES AND 
FLOUNDERS. 
A STUDY IN ADAPTATION. 
WO groups of our 
Titec fishes that are 
very highly adapted 
to life on the sea bottom 
are the flounders and the 
skates. While these 
groups are about as wide- 
ly separated in their re- 
lationships as fishes can 
be, they have both been able to solve very suc- 
cessfully the problem of adaptation to similar 
conditions. However, they have been compelled 
to do this in very different ways, for the skates 
are relatives of the sharks and have undergone 
a process of evolution in which the rounded body 
of the shark has assumed a greatly depressed or 
flattened form, while the flounder is a bony fish 
with a body greatly compressed from side to 
side. Its ancestors swam after the ordinary 
manner of fishes, but in order to adapt them- 
selves to the bottom were compelled to lie on one 
side. Any similarities of form or habit between 
the flounders and skates must therefore be mere- 
ly cases of resemblances produced in the attempt 
to suit themselves to the same conditions of life. 
The changes that have come about in these fishes 
during this process of adaptation are worthy of 
our consideration. 
The skates or rays (sub-order Batoidei or 
Rajida), are a modified offshoot of the sharks, 
(Elasmobranchi), that have assumed a life on 
the sea floor instead of swimming in its upper 
Their food, for the 
most part, consists of those animals which are 
waters like their relatives. 
either sessile or move but slowly, and in most 
cases their teeth are adapted to crushing the 
shells of molluses and other animals with ex- 
ternal skeletons. 
When we examine a skate we find a thin disc- 
like body with a broad head, very broad lateral 
fins, and a long, slender tail, which in some cases 
is so narrow and long that it forms a whip-like 
member. Viewed from the under side the head 
shows a number of peculiarities. As the food 
is obtained on the bottom the mouth is on the 
underside of the head so that the food may be 
obtained without changing the position of the 
body more than is necessary to bring the mouth 
over the food. The nostrils also are placed well 
