Reb Boruch, it is a pleasure to hear from you again after a long time.

1. The Teshuvos Sho'el u'Meshiv (Mahadura Kama, part 2, end of Siman 110, DH v'Hinei Talmidi) writes that the Toras Kohanim is the source for the statement of Rashi in Parshas Emor that "all the congregation stoned him" means that this happened in the presence of the entire community, but the addition in Rashi -- that one learns from here that Shelucho Shel Adam Kemoso -- is not stated in the Toras Kohanim. The Sho'el u'Meshiv writes that in fact there are two distinctions between the case of Mekalel and the standard case of Shelucho Shel Adam Kemoso:

a. In the case of Mekalel, it was "b'Ma'amad Kol ha'Edah" -- in the presence of all the congregation. Since everyone was present, one can argue that it is not necessary for everyone actually to stone him, but rather it is sufficient that they merely be present at the time of his execution, and this is considered as if they actually carried out the execution. It follows that one cannot derive Shelucho Shel Adam Kemoso for all areas of the Torah from the law of Mekalel; the reason why, in that case, they are all considered to have executed him is that they were all present at the time. Hence, one still has no proof that Shelucho Shel Adam Kemoso applies when the person who sent the Shali'ach is not present at the time the Shelichus was carried out.

b. The other reason for why it is not possible to derive Shelucho Shel Adam Kemoso from the case of Mekalel is based on a principle that "Ein Danin Efshar mishe'Iy Efshar" -- "we may not derive something that is possible from something that is not possible" (see, for example, Yevamos 61b). It is impossible for all of the congregation to execute the Mekalel, but it is possible for all of Klal Yisrael to slaughter the Korban Pesach. Even according to the opinion (Rebbi Yehudah, Pesachim 91a) that one may not slaughter the Korban Pesach for a single person, one may slaughter it for one's family because a family is considered a group (Rabim), not an individual, and thus it would be possible for every family to slaughter the Korban Pesach.

2. Based on the above explanation, we now have an answer to your question of why Rebbi Akiva Eiger did not write "Tzarich Iyun" in Kidushin 41b. This is because the Gemara there could not have derived Shelucho Shel Adam Kemoso from Mekalel as a result of distinctions (a) and (b) above. However, once we know the principle of Shelucho Shel Adam Kemoso from the Limud from Korbon Pesach, we now may say that the case of Mekalel is another example of this principle.

It follows that there is no contradiction between Rashi in Parshas Bo and Rashi in Parshas Emor, because the source for this Halachah is Korban Pesach, as the Gemara says in Kidushin, but after we have derived it from there, Mekalel is also an example of this, as Rashi writes in Emor.

Kol Tuv,

Dovid Bloom

Here are further explanations and sources for the distinction that we made in the first answer between the standard concept of Shelichus and the special type of Shelichus that happens when the Meshale'ach is actually there watching his Shali'ach doing the action:

1. I found the following idea in a new Sefer, "Shenayim Mikra," a collection of Divrei Torah on the Parshiyos written by the author of Talelei Oros (who died at a young age a few years ago). On the verse in Parshas Emor, "And all the congregation will stone him," he first points out that in some editions of the Chumash the Girsa in Rashi starts, "In the presence of all the congregation," and then the next word, "mi'Kan" -- "from here" -- is in parentheses, followed by "she'Shelucho Shel Adam Kemoso." This fits well with what we said in our first answer, because it implies that we indeed cannot derive "from here" to the entire Torah that Shelucho Shel Adam Kemoso, because this case is different as the entire Eidah is present. However, it does work with "Shelucho Shel Adam Kemoso," as Rashi in Parshas Emor concludes, because even though this is a different type of Shelichus than the ordinary type, it is still a form of Shelichus. We just cannot learn this principle "mi'Kan," from "v'Ragmu," to the rest of the Torah.

2. The author then cites a law in Hilchos Milah (Shulchan Aruch YD 265:9) that "the father of the son stands next to the Mohel to inform him that he is his Shali'ach." It is a Chidush that the father must stand next to the Mohel, because, in general, once he told the Shali'ach to do something for him, the Shali'ach now may do it wherever he likes. The Vilna Ga'on there (#40) writes that the reason why the father must stand next to the Mohel is that Milah of a baby boy is similar to a Korban, and when someone brings a Korban he must stand next to the Kohen when he offers it. However, we now may give a different reason for why the father must stand next to the Mohel: by the father being together with his Shali'ach, the Shelichus is stronger and is similar to what Rashi writes at the end of Parshas Emor, that since everyone is present it is a stronger Shelichus than the Shali'ach alone going away and acting for his Meshale'ach.

3. I once heard a very interesting insight in the name of Rav Leib Gurwicz zt'l, the Rosh Yeshiva of Gateshead, which reveals more about this stronger form of Shelichus. The Rosh Yeshiva cited the Gemara in Gitin (beginning of 67b) which states that if a man told ten people to write a Get, one of the 10 may write it on behalf of all of them. However, if he said, "All of you write it," then one of them must write it in the presence of the other nine. We learn from this that if everyone is present, this is a stronger form of Shelichus. (I think that the Pshat may be that if all ten are present, then it is considered as though everyone is doing the action of writing the Get, because in practice it is not possible for ten people to write a Get together, so when the man said that they should all write it he meant that they should all do something to take part in its writing. The only thing that ten people can do to write a Get together is to be present at its writing and ensure that it is written properly.)

4. We find also that the Ramban (end of Parshas Lech Lecha) describes how Avraham Avinu performed Bris Milah for all the members of his household. The Ramban writes that Avraham was eager to do the Mitzvah and thus performed Milah himself for all of the members of his household. The Ramban adds that it is possible that Avraham did not actually Mal every single one himself, but rather he arranged that many Mohalim should come and perform the Milos, with Avraham Avinu standing over them. The fact that the Ramban writes that Avraham stood over the Mohalim is a proof for the ruling of the Shulchan Aruch cited above that the father should stand next to the Mohel. That is, since the father does not know how to perform the Bris himself, he asks a Mohel to do it for him. However, the fact that the father stands next to the Mohel makes it as though the father is doing the Milah himself and the Mohel is merely his "long arm." Similarly, it was not possible for Avraham Avinu to do the Milos of all of the males of his household because of his age, but since he stood over the Mohalim it was equivalent to him doing it himself.

5. We have now found another proof for Rav Gurwicz' explanation of Rashi at the end of Parshas Emor. It is not physically possible for all of the congregation to execute the criminal. However, by being present at his execution, they did the maximum that they could do, and thus all of Klal Yisrael was considered to have performe the Mitzvah of killing the Mekalel. This is stronger than what happens with the Korban Pesach, where the Korban is slaughtered with the agreement of everyone, and thus everyone has a part in the Mitzvah, but it is not considered as though everyone everyone actually participated in the physical act of Shechitah.

6. We may add another support for Rav Gurwicz' explanation: the fact that the Gilyon ha'Shas (Kidushin 41b) has no "Tzarich Iyun" on why the Gemara does not cite the verse from the end of Parshas Emor. He is not bothered by this problem because that verse teaches a stronger type of Shelichus, and if we would have had only the verse at the end of Parshas Emor, we would not have known the Halachah that Shelucho Shel Adam Kemoso applies even when the Shali'ach is not present when the Shelichus is carried out.

7. Here is another explanation given by the Acharonim for the difference between the Shelichus discussed in Kidushin 41b and the Shelichus mentioned by Rashi at the end of Parshas Emor. This explanation is given by the Panim Yafos (the author of Sefer ha'Makneh on Kidushin and Hafla'ah on Kesuvos) on Parshas Emor:

a. The Panim Yafos explains that the Shelichus mentioned by Rashi at the end of Parshas Emor is really "Arvus" (as derived by the Gemara in Sanhedrin (27b) from the verse, "And each person will stumble on his brother" (Vayikra 26:37), which teaches that all of Klal Yisrael are responsible for each other, as the Gemara in by the Gemara Sanhedrin end 27b). The Mishnah in Berachos (34b) states that if the Shali'ach Tzibur errs in his prayers, this is a bad sign for the community, because "Shelucho Shel Adam Kemoso." Even though the Mishnah uses the phrase "Shelucho Shel Adam Kemoso," its meaning there differs from its meaning in the Gemara in Kidushin. In Kidushin, the Gemara discusses cases such as a Shali'ach who brings a Get to a woman, which is clearly not an obligatory Mitzvah. The Gemara in Kidushin is referring to the type of Shelichus wherein the Shali'ach can make a "Chalos" for the Meshale'ach -- he can make the Ma'aseh of Kidushin or Gerushin take effective. In contrast, in the case in Berachos, a group of people have a Mitzvah to perform together -- Tefilah -- and the Shali'ach Tzibur is able to discharge their obligation with his Tefilah. Similarly, in Parshas Emor, the entire congregation had a Mitzvah to kill the Mekalel, but since they cannot all do this act they made a Shali'ach to do it; this was an act of Arvus.

b. The Panim Yafos questions his explanation from the fact that Klal Yisrael did not accept upon themselves Arvus for each other until they crossed the Jordan River to enter Eretz Yisrael at the end of the 40 years in the Midbar (see Rashi to Sanhedrin 43b, DH v'Harei). How, then, could there have been a Mitzvah of Arvus to kill the Mekalel for what he did in the Midbar?

c. The Panim Yafos answers that since all of Yisrael possess one root (as we say in the Shemoneh Esreh of Minchah on Shabbos, "And who is like Your people Yisrael, one nation in the land"), it follows that even before there was an obligation of Arvus there was already a Mitzvah on all of the people to administer a punishment to someone who went against Hash-m.

d. In summary, even though the term "Shelucho Shel Adam Kemoso" is used both in Kidushin (41b) and in Berachos (34b), it has a different meaning in each place. In Kidushin it means what we generally refer to as Shelichus, while in Berachos it means Arvus. Similarly, Rashi in Parshas Emor is referring to the Arvus- type of Shelichus. Therefore, the Gemara in Kidushin could not have derived Shelichus from Parshas Emor, because there it is a different kind of Shelichus. For this reason, the Gilyon ha'Shas did not ask a "Tzarich Iyun" from there; he knew that there is a difference between the two types of Shelichus.

Kol Tuv,

Dovid Bloom