In the lecture, the professor casts serious doubts on the article and maintains that none of the theories about how agnostids may have lived mentioned in the reading paragraphs are convincing. The professor presents several evidences as follows to illustrate her opinions.
The first point retorted by the professor is as to the theory of free-swimming predators. She asserts that other types of primitive arthropods swam in the open ocean were equipped with well-developed eyes, which enabled them to track preys. Nonetheless, agnostids' eyes were poorly developed eyes and even blind eyes, meaning that they were not active predators in the ocean. Worse, according to fossil records, agnostids did not have any special sensory organs to help them find prey. In contrast, the author's viewpoint seems flawed.
Secondly, in terms of the hypothesis of seafloor dwellers, opposite to the reading material, the professor points out that seafloor dwellers usually do not move fast or move very far in the seafloor and tend to live in localized area rather than new areas. This indicates that seafloor dwellers often occupy a small geographic area. However, according to some solid scientific evidence, agnostids lived in multiple geographic areas and moved from one place to another in long distance. Thus, it is impossible for agnostids to be seafloor dwellers, which directly contradicts the author's statement.
Finally, the professor believes that parasite theory cannot hold water either, because parasites' population is not very large and has upper limits. This lies in the fact that if parasites' population is very large, they would kill off the host organism that they live on. Besides, it has already been proved that agnostids' population was very large, because various species of vast amounts of agnostids' fossilized individuals have been discovered. Therefore, agnostids could not be parasites.
In sum, the author's opinions toward three hypothesis about how agnostids lived are totally disproved by the professor.