Step 1: Understanding the Concept: 
This question compares two "constitutional" theories of personality, which link body type (physique) to temperament. We need to match Sheldon's "ectomorph" with its equivalent in Kretschmer's system. (Note: "Asthetic" is a common misspelling of "Asthenic"). 
Step 2: Detailed Explanation: 
Let's compare the typologies: 
    
 William Sheldon's Somatotypes:
        
            
 Ectomorph: Thin, linear, fragile body. Associated with cerebrotonic temperament (introverted, anxious, thoughtful).
            
 Mesomorph: Muscular, athletic body. Associated with somatotonic temperament (assertive, adventurous).
            
 Endomorph: Round, soft body. Associated with viscerotonic temperament (sociable, relaxed).
        
    
 Ernst Kretschmer's Types:
        
            
 Asthenic (or Leptosomic): Thin, lean, narrow body. This is the direct parallel to Sheldon's ectomorph.
            
 Athletic: Muscular body. Corresponds to mesomorph.
            
 Pyknic: Plump, round body. Corresponds to endomorph.
        
Based on this comparison, Sheldon's ectomorph (thin build) is similar to Kretschmer's asthenic type. 
Step 3: Final Answer: 
Sheldon's ectomorphy type corresponds to Kretschmer's asthenic (asthetic) type.