Explanation #1 (Rashi): There is no concern lest they laugh at them and they will come to carry [the bells].

Question: In any case we should be concerned lest they break and they will come to carry them, like we say above (58a) about a slave, that he may not go out with a signet on his neck!

Answer: Here we discuss [bells] hung on a chain. They do not break off.

Explanation #2 (Riva): The Yerushalmi establishes it to discuss minors. Even if it breaks and they come to carry it, there is no Isur.

Note: This connotes that there is no Isur at all, not even due to Chinuch. Perhaps this is like the answer in Tosfos (Nazir 28b DH Beno) that Chinuch applies only to doing Mitzvos, but not refraining from Isurim.

Citation (Yerushalmi): Ze'ira says, with a bell on his neck. How do we explain "every person" in our Mishnah? Both rich minors and poor minors.

Citation (cont.): Our Mishnah argues with Ze'ira. It says "not with a bell on his neck"! [Rather,] this refers to adults, and this refers to minors.

Explanation: It says "not with a bell on his neck" regarding adults, lest it break and they come to carry it. It permits here regarding minors, for whom there is no concern, like I explained.

Question: Still, why did it mention princes, since there is no concern if a minor overtly carries it?

Answer: If not [that all Yisrael are] princes, people would constantly laugh at him, and it is impossible that his father will never hear, and his father will take it in his hand, and he will come to carry it;

However, if [all Yisrael are] princes, they will not laugh. If so, even if it breaks there is no concern lest his father take it, for it is not common that his father will be there at his side at the time it breaks.

Explanation #1 (Rashi): Even though he did not find out in between, we say that the days in between are a Yedi'ah to separate, for it is impossible that he did not hear in between that that day was Shabbos, just he did not remember the Melachos.

Question #1 (R. Eliezer): It says in the Gemara (below, 71a) that if he harvested and grinded b'Shigegas (forgetting that it is) Shabbos and Zadon Melachos (he knew that they are forbidden on Shabbos), and returned and harvested and grinded b'Zadon Shabbos and Shigegas Melachos, [the first] harvesting is Gorer (drags with it the second) harvesting (to get atonement on the same Korban), and grinding is Gorer grinding, i.e. he is liable only once;

We discuss on one Shabbos, for in two Shabbosos he is liable twice, for the days in between are a Yedi'ah to separate;

Inference: Even though it became known to him before the latter harvesting that the day was Shabbos, for [the latter time] he harvested and grinded b'Zadon Shabbos, even so it is not [considered] a Yedi'ah, and it is considered one Helam, since he did not know that he sinned, for he thought that the Melachah is permitted;

The reason is because it says "Oh Hoda Elav Chataso" - he will have Yedi'ah of the sin.

Question #2 (Rivam): In the Gemara we learn from a verse. According to Rashi, that it is impossible that he did not hear in between, why do we need a verse?

Question #3 (Ri) Citation (Kerisus 16a - Mishnah - R. Akiva): I asked R. Eliezer, if one did many Melachos on many Shabbosos resembling one Melachah... [R. Eliezer] said he is liable for each one. We learn from a Kal v'Chomer from Nidah...

Amora'im argue there in the Gemara about his question, and it says at the end of the Sugya "according to Rav Chisda, who says that he asked about Shigegas Shabbos and Zadon Melachos, whether or not the days in between are a Yedi'ah to separate, regarding Nidah, what days in between are there?"

It answers that he had Bi'ah with her and she immersed, and saw [Dam Nidah], and he had Bi'ah with her again. There, even if she delayed several years and did not immerse, it is considered all one Helam!

Explanation #2: Rather, when she immersed, the days of Heter in between, even though he did not know, it is as if he knew. Also here, regarding Shabbos, even though he did not hear about the days of Heter in between, they are a Yedi'ah to separate, for it is a Gezeiras ha'Kasuv that there be a Shemirah for every Shabbos!

Question: There, R. Eliezer learns Shabbos from Nidah. Just the contrary, a verse is written regarding Shabbos, and not regarding Nidah!

Answer (Ri): This that we learn from a verse in the Gemara, this is according to R. Elazar b'Ribi Shimon there, who says that R. Akiva did not ask R. Eliezer about this, rather, about one who had Bi'ah with a Nidah, and [R. Eliezer] answered that he is liable for each [Bi'ah], based on a Kal v'Chomer from Shabbos.