What animal does Ponyboy dissect?

In Chapter 1, Ponyboy is describing how the Socs are different from the Greasers. He mentions that the Soc girls looked down on the Greasers and treated them like they were dirt. Later on that night, Ponyboy is doing homework and starts thinking about how the character Pip from the novel Great Expectations is similar to the members in the Greaser gang. Pony says that Pip also felt lousy when he was looked down upon by others because he wasn't a gentleman. Pony then comments about a time in biology class that he was looked down upon by a girl. In class, Ponyboy had to dissect a worm, and he took out his switchblade to cut it open because the razor the teacher gave him was dull. The girl who was sitting beside Pony gasped and told him, "They are right. You are a hood" (Hinton 14). Ponyboy then mentioned that her comment didn't make him "feel so hot."