using collect on a ReadStream

Hi,

I get a ReadStream from some part of a program which is
created this way

stream := (ReadStream on: #( #(#a #b) #(#b #c))) 

I like to use collect: on that stream:

stream collect: [:each| 'k',each first]

Is there a possibility to specify the resulting collection
produced by collect. The problem here is the species 
call with an add: call afterwards which is not appropriate
(the debugger said :) )

thanks,

Norbert