Clicking to add content is adding it outside of the page's table

Rails
1

Clicking the “add” button in my nested form is adding the content
outside of the page’s main table, how can I get it to add the html
into the table that the link is contained in?

I followed the Railscast

My view file:

<% echantillon_form.fields_for :treatments do |builder| %> <%= render :partial => "treatment_fields", :locals => {:f => builder} %> <% end %> 
  <%= link_to_add_fields "Add treatment",

echantillon_form, :treatments %>

  <%= echantillon_form.submit "Submit" %>
  <% end %>

and my partial:

<%= f.label(:treatmenttype, "type de traitement") %> <%= f.text_field :treatmenttype %> <%= f.label(:treatmenttype, "commentaires sur la preparation") %> <%= f.text_field :preparation %> <%= f.hidden_field :_destroy %> <%= link_to_remove_fields "remove", f %>