I thought the copy ctor always takes the form
Test::Test(const Test & arg);
for a class Test.

But I read the following sentence in Stanley Lippman's C++ Primer 4th
Edition(Page 476):

The copy constructor is a special constructor that has a single
parameter that is a (usually const) reference to the class type.

My doubt
--------------
Since the above sentence contains "(usually const)" in parantheses,
does it mean that we may need a copy ctor that takes the form
Test::Test(Test & arg) ?
(that is, reference to plain type) ?

Kindly let me know when we will need this second form.

Thanks
V.Subramanian