remove( vertex ) {

		if ( vertex.prev === null ) {

			this.head = vertex.next;

		} else {

			vertex.prev.next = vertex.next;

		}

		if ( vertex.next === null ) {

			this.tail = vertex.prev;

		} else {

			vertex.next.prev = vertex.prev;

		}

		return this;

	}
Removes a vertex from the linked list.

@private
@param {VertexNode} vertex - The vertex to remove.
@return {VertexList} A reference to this vertex list.