Context:

"The nervous system was so complex and highly developed as to leave Lake aghast. Though excessively primitive and archaic in some respects, the thing had a set of ganglial centres and connectives arguing the very extremes of specialised development. Its five-lobed brain was surprisingly advanced; and there were signs of a sensory equipment, served in part through the wiry cilia of the head, involving factors alien to any other terrestrial organism."

(Source)

I think that 'to be' verb should be involved:

Factors ARE alien to any other terrestrial organism

Questions:

1. Why didn't the author use 'to be' verb in the sentence?

2. If it's optional- could you please explain these options to me?

Context:

"The nervous system was so complex and highly developed as to leave Lake aghast. Though excessively primitive and archaic in some respects, the thing had a set of ganglial centres and connectives arguing the very extremes of specialised development. Its five-lobed brain was surprisingly advanced; and there were signs of a sensory equipment, served in part through the wiry cilia of the head, involving factors alien to any other terrestrial organism."

(Source)

I think that 'to be' verb should be involved:

Factors ARE alien to any other terrestrial organism

• Oxford's elaboration of the definition (2.Unfamiliar and disturbing or distasteful)

Questions:

1. Why didn't the author use 'to be' verb in the sentence?

2. If it's optional- could you please explain these options to me?

Sentence:

Factors alien to any other terrestrial organism (from book)

I think that 'to be' verb should be involved

Factors ARE alien to any other terrestrial organism

Questions:

1. Why didn't the author use 'to be' verb in the sentence?

2. If it's optional- could you please explain me these options

Context:

"The nervous system was so complex and highly developed as to leave Lake aghast. Though excessively primitive and archaic in some respects, the thing had a set of ganglial centres and connectives arguing the very extremes of specialised development. Its five-lobed brain was surprisingly advanced; and there were signs of a sensory equipment, served in part through the wiry cilia of the head, involving factors alien to any other terrestrial organism."

(Source)

I think that 'to be' verb should be involved:

Factors ARE alien to any other terrestrial organism

Questions:

1. Why didn't the author use 'to be' verb in the sentence?

2. If it's optional- could you please explain these options to me?