Suddenly Dr. Villiers stiffened, and a low growl escaped his lips. Marcy felt the cock start to pulse, and frightened, tried to pull away. But as she began to turn her head, he pressed down, flattening his testicles against her chin and lower lip, and holding her fast with his hairy thighs.

"No, X-999, you must swallow it or the experimental data will be incomplete. You have hired out to engage in important research, and you must not hesitate to carry out each act to fulfillment, or you will invalidate the results," Dr. Villiers explained unemotionally, as his cum flooded her mouth.

Marcy swallowed, and the warm liquid shot down her throat. At the same moment she felt her own orgasm beginning. The lips of her cunt contracted, and the muscles deep inside spasmed, sending fresh moisture to dampen her thighs.

The doctor made a clucking sound. "Most interesting. Experimental Animal X-999 is capable of achieving orgasm without actual physical stimulation of the genital area. Apparently it occurred merely from the pleasure of sucking my cock." He released her head and stared at her thoughtfully. "This is quite fascinating, my dear, and leads me to the hypothesis that you derive more pleasure from serving than from being served. You will tend to be high up on the Sado-Masochist Scale, tending toward the Masochist end."

Marcy raised a shaky hand to wipe at her sticky lips, but Dr. Villiers intercepted it. "No, that would contaminate the sampling. You must swallow all my seed!"

"But…"

Villiers hit her twice with his open palm, rocking her head from side to side. "You are not permitted to talk back during experiments! You will be taught many things pertaining to the nature of your psyche while you are here, but you are not to comment on them! Do you understand?"