Option 1: Morely - This option refers to John Morley, a British politician and writer. There is no specific information provided to suggest that Morley called the Prime Minister "Primus inter pares."

Option 2: Harcourt - This option refers to Sir William Harcourt, a British lawyer and politician. There is no specific information provided to suggest that Harcourt called the Prime Minister "Primus inter pares."

Option 3: Laski - This option refers to Harold Laski, a British political theorist and economist. There is no specific information provided to suggest that Laski called the Prime Minister "Primus inter pares."

Option 4: Lowell - This option refers to A. Lawrence Lowell, an American educator and legal scholar. There is no specific information provided to suggest that Lowell called the Prime Minister "Primus inter pares."

The correct answer is option 1 - Morely. However, it should be noted that there is no specific information provided in the question to support this answer.