Summer soon arrives. The olive trees grow heavy with fruit, butterflies lay eggs, and tree frogs sing as evening falls. A man named Peter arrives to tutor Gerry. He's difficult at first but after a few weeks, the island calms him and he becomes more forgiving. He agrees to teach Gerry English by letting him write a book, so Gerry spends an hour every morning working on a narrative about the family traveling around the world to capture animals. Peter and Margo both become suddenly interested in botany, so they take walks in the garden while Gerry writes.
Note here that the assertion that Peter and Margo become interested in botany is entirely Gerry's belief—one that betrays the fact that he's a child who believes that there's nothing more interesting than the natural world and therefore ignores the truth that Peter and Margo are romantically involved. This also shows that Gerry's first inclination is to believe that others think about the natural world the way he does.
After the scorpion debacle, the family gives Gerry a room to house his animals. Gerry calls it his study and he keeps his collections of eggs, insects, and other preserved specimens, such as a four-legged chicken, in it. When Gerry finds a bat, he takes it upon himself to stuff it and hang it on the wall. He's very proud of it, but the bat soon seems to feel the heat of summer. It sags and begins to smell. Gerry is very annoyed when the family finally figures out the smell is coming from the bat and makes him get rid of it.
The bat becomes a symbol for Gerry's incomplete education and bursting enthusiasm regardless. Just as with Gerry's misinterpretation of Margo and Peter's motives, his annoyance at his family shows that he finds it ridiculous that they're not willing to put up with the natural world and the natural process of decomposition.
Peter offers to show Gerry how to properly preserve animals if he can find another specimen, so Gerry begins trying to hunt bats with a bamboo stick at night. He's unsuccessful in his quest but sees a number of other interesting night creatures while he hunts. Gerry vows to capture squirrel dormice and so spends his days thrusting his hands into hollow trunks to search for sleeping ones. One day, he pulls out a bewildered Scops owlet and carries him home. The family has no objections to keeping the owl, and they decide to name him Ulysses. Even though he's tiny, Ulysses is fearless and will attack anything.
Though owls are dangerous in very different ways than scorpions are, they're still fairly dangerous animals. The family's willingness to keep Ulysses then shows that deciding whether an animal is dangerous or not is often a matter of perception—the family has possibly not been around owls or has simply heard or experienced more when it comes to the danger of scorpions.
Gerry sets Ulysses up in the drawing room and decides that he and Roger should be introduced. He puts Ulysses on the floor and instructs Roger to make friends. Roger seems nonplussed when Ulysses turns his head all the way around. Finally, Roger belly crawls to Ulysses and pokes him with his nose, which turns out to be a mistake. Ulysses digs his claws into Roger's nose, and Roger refuses to come out from under the table until Ulysses is back in his basket.
Though Roger certainly appears curious, it's important to keep in mind that he approaches Ulysses primarily because Gerry asked him to and he wants to please Gerry. This shows again how close of a friendship Gerry and Roger have. When Roger gets hurt, it impresses upon Gerry and the reader that Gerry has all the responsibility to keep Roger safe.
As he grows, Ulysses takes up residence in Gerry's study. He spends the day sleeping and when night falls, he wakes up, regurgitates his daily pellet, and sits with Gerry for a moment before asking for the shutters to be opened. Then, Ulysses flies out to hunt. He and Roger become friendly with each other and occasionally, Ulysses will ride on Roger's back down to the sea for an evening swim.
The strange understanding that Ulysses and Roger come to shows that when humans orchestrate such a relationship, entirely unrelated animals can become friends and form relationships just like humans can.
Larry, Peter, Margo, Leslie, Gerry, and Roger begin taking the family boat, the Sea Cow, down to a small bay nightly to swim, sit on the warm rocks, and escape the sun. One night, as Gerry floats, he feels ripples and hears a sigh. He notices that he's far away from shore and is afraid of what's in the water, but he realizes it's a porpoise. Eight porpoises surround him and swim with him before heading out to open water. After this, the porpoises visit regularly. The family also discovers that the sea is full of phosphorescent (glowing) life during the hot months, and to add to the effect, fireflies dance around the bay too.
This evening bathing suggests that the Durrell children at least are adapting to the local customs of Corfu, given that they aren't bathing in the in-house bathroom. The phosphorescence in particular shows that even for those less convinced (such as Larry), the natural world can still be a spectacular place that is capable of providing a great deal of entertainment.
Mother envies her children their swims, though she insists she's too old when they invite her along. Finally, she purchases a strange, heavy, frilled bathing costume. When she tries it on, she calls everyone upstairs to see it. Roger is the first to enter her room and he races right back out, barking at the costume. Nobody likes it. Mother refuses to find another suit, so the family plans a picnic and invites Theodore.
Gerry's decision to include far more of Roger's thoughts on the suit than his siblings' thoughts shows again how much he prioritizes his animals over people. Further, it shows that he does his best to listen to and interpret what his animals say in order to better understand them.
On the day of the picnic, Theodore points out that there will be no moon. After arguing, everyone decides to go anyway, so they load into the Sea Cow and head down to the bay. When they reach the bay, Mother wades into the water. As she does, Roger becomes excited and attacks her costume by grabbing hold of one of the ruffles. He pulls, pulling Mother down into the water. The ruffle comes loose, which excites Roger further. As the rest of the family laugh uproariously on the shore, Mother tries to beat Roger off and keep some of her costume intact. Finally, Theodore rescues her.
Mother's willingness to join her children for their swim suggests that she's trying to take on and accept some of the island's local customs, especially if it means she gets to spend more time with her children. Roger's actions here show that he has no time for human customs that he deems ridiculous, showing again that individuals' responses to absurd happenings are what sets people apart.
The phosphorescence is magnificent that night. After swimming, everyone congregates on the shore to eat. Then, as if on cue, the fireflies begin to dance and the porpoises appear, looking as though they're on fire as they swim through the phosphorescence. Gerry can even see the trails of phosphorescence underwater where the porpoises swam. This goes on for an hour until the porpoises head back out to sea.
Gerry's description of the show again shows that the natural world can be seen as amazing by everyone, assuming they want to see it as such. This is surely a proud moment for Gerry, as it suggests that his family is, at times, just as entranced by nature as he is.