In embryonic development, cells undergo a gradual process of specialization where they move from a flexible potential to a fixed fate. When cells from one prospective tissue are transplanted to a different environment yet retain their original fate, specific terms describe their developmental state.

The scenario where prospective skin cells transplanted near future muscle cells still differentiate into skin cells illustrates a key concept in developmental biology: cell determination. Determined cells have irreversibly committed to a specific fate, meaning their developmental pathway is fixed. These cells will differentiate into their destined tissue type regardless of environmental changes or relocation.

Determination is distinct from commitment, which can be an earlier, reversible stage where cells are biased but can still change fate depending on extrinsic signals. Totipotent cells, on the other hand, are the earliest embryonic cells that can generate any cell type including all embryonic and extraembryonic tissues. Differentiated cells have completed specialization, exhibiting the structure and function characteristic of a mature cell type.

In an embryonic transplantation experiment, the behavior of transplanted cells reveals their developmental status. If prospective skin cells transplanted near muscle cells still become skin, they are determined—they have passed the point of reversibility and cannot respond to new signals to become muscle. This contrasts with committed cells, which may still change fate if exposed to different cues.

In summary, the transplanted cells that differentiate into skin despite being near future muscle cells would be described as determined. This state indicates a stable developmental program that is not influenced by the new environment.

Hence, the correct answer to the query is:

(1) Determined

This article explains the concept of cell determination and how embryonic transplantation experiments help identify the point at which cells lose plasticity and adopt an irreversible fate. Understanding these stages is essential for developmental biology, regenerative medicine, and stem cell research.