We are in chapter 5 of Maseches Temurah, mishnah 2. In the previous mishnah we learned two cases:
A person who was obligated to bring one olah, and who owns an animal that is about to give birth to a firstborn. We learned that he may act first and be makdish the offspring while it is still in its mother's womb, saying: "If it will be a male, in place of its being a firstborn - let it be an olah," and in that way he can bring it as an olah, and the hekdesh takes effect.
The mishnah then moved on, without any indication that it was switching cases, to a new case: according to the Bartenura, a pregnant chatas whose owner said, "If what is in her womb is a male - let it be an olah, and if a female - let it be a shelamim." And the mishnah ruled that even if both were born, each one takes on the status of hekdesh that was designated for it.
The third case: a pregnant non-sacred animal:
Here the mishnah continues with the same type of situation, in which a person seeks to use the offspring of his pregnant animal in order to fulfill his obligation to bring a korban. But once again, without any marker, the mishnah moves to a third case. According to the Bartenura, and this also emerges from the Gemara, we are dealing here with a non-sacred animal that was never made hekdesh at all - this is not a chatas but an ordinary animal that is pregnant - and its owner is obligated in only one korban and not in two.
Let us say that he has to bring one olah, or one shelamim as in the previous case. What will the law be when two males or two females come out? After all, he did not seek to bring two olos but only one, and when he said, "If what is in there is a male - let it be an olah," he meant one and not two, for why would he be makdish a second olah unnecessarily? This is the underlying assumption of the first part of our mishnah.
The mishnah says: "Yaldah shnei zecharim - echad mehen yikrav olah, ve'hasheini yimacher lechayavei olah u'damav chulin" - if she gave birth to two males, one of them is offered as an olah, and the second is sold to those obligated to bring an olah, and its proceeds are non-sacred.
Let us review the case: a person has a pregnant non-sacred animal, and he is obligated to bring an olah. He said: "If what is in there is a male, let it be an olah." The animal gave birth to two males. His olah is indeed in his possession, but now two animals stand before him and he does not know which of them is the olah - one of them is consecrated as an olah and the other remained non-sacred.
In explaining the mishnah we are following the Bartenura. Although he does not say explicitly that there is a doubt here, this necessarily emerges from his words, and this is also the approach of Rashi: he has a doubt on his hands. Two animals, one an olah and one not, and he does not know which is which. Therefore one of them he can bring as his olah, and the other he cannot; he must find a buyer and sell it to him, and the money he receives in exchange is non-sacred money, and is not consecrated.
How this is done in practice:
He has two newborn animals, eight days old, two male lambs. He wants to bring them to the Beis HaMikdash so that only one of them will serve as an olah, and the value of the second he wishes to put into his own pocket. The difficulty is that he does not know which of the two animals is his olah and which remained non-sacred.
What should he do? He should go up to the Beis HaMikdash, stand at the entrance and look for another person who also wishes to bring an olah. He should say to him: "Let's make a deal. I have two animals, one of them non-sacred and one of them an olah, and I do not know which is which. One of them is my olah, and the second I wish to sell to you. If you pay me for the non-sacred animal - whichever of the two it may be - I will give it to you for an olah, and you will have an olah to bring, and I will even give it to you at a discount."
Let us say, for the sake of discussion, that he sold it to him for fifty dollars, a considerable discount on a day-old lamb. The buyer agrees, and the two of them make a condition: whichever of the two animals is the one that has not been consecrated until now - that is the one I am buying, and that one, whichever of the two it may be, I am consecrating as my olah. In this way both animals are now certainly consecrated as an olah. True, we do not know which animal belongs to which owner - which is the one the first owner consecrated and which is the one he sold - but that makes no difference.
The two of them together bring the two animals to a kohen in the Beis HaMikdash and say: "These are our two animals, and they have become mixed up. We do not know which one belongs to whom, but offer both of them on our behalf, and whoever the owner is - the merit will go to him." And in this way the matter works out well.
Why the money is chullin:
The Mishnah's intent in stating "ve'damav chullin" - and its money is chullin - is this: whichever of the two animals was not the consecrated one is an ordinary chullin animal and is not sanctified at all, and a person may sell it to his fellow. The money he receives in exchange for it is an ordinary sale price, and the matter has no connection whatsoever to redemption of consecrated property. Therefore the money is completely chullin, and the seller - the owner of the animal that gave birth to the twins - keeps the money for himself.
And since this is so, and since we are dealing with chullin, it is clear that this is not the case of the previous Mishnah, which deals with a pregnant consecrated animal. For with a pregnant consecrated animal there is no possibility at all that the offspring will not be sanctified. True, we learned that the sanctity can be shifted from one status to another, but that it should have no sanctity at all is impossible. It necessarily follows that our Mishnah is dealing with a chullin animal. This is the first case in this Mishnah.
"Yaldah shtei nekeivos":
The Mishnah continues: "Yaldah shtei nekeivos - achas mehen tikrav shelamim, ve'hasheniyah timacher lechayavei shelamim u'demeihen chullin" - if it gave birth to two females, one of them is offered as a shelamim, and the second is sold to someone obligated to bring a shelamim, and their money is chullin. That is, when two female animals emerge from the mother, and he had said: "If what is there is a female fetus, let it be consecrated as my shelamim" - one of them is offered as a shelamim and it is his, and the second is sold. The exact same arrangement, since he obligated himself in only one shelamim, and it is clear that he did not intend to consecrate both of them.
This is unlike the previous Mishnah, where he said "if it is a male - it shall be an olah, and if a female - a shelamim," and there it is evident that he wanted both and had an interest in both. Here he had no interest in two shelamim offerings, so why would he consecrate an additional animal? Therefore the law is the same: two females, one is a shelamim and one is not, and it is not known which is which. He brings both of them to the Beis HaMikdash, finds a person who is obligated to bring a shelamim, and makes the same conditional deal with him.
That animal which has not been consecrated until now - that is the one he will buy and that is the one he will consecrate, and the two of them will bring the two animals together, as a pair, to the kohen. The kohen will offer both of them on behalf of both of them, and whoever the owner is - the merit will go to him. And in this way the matter works out well. And here too "u'demeihen chullin" means that the seller keeps the money for himself, since he sold an ordinary chullin animal.
"Yaldah tumtum ve'androginus":
The next case in the Mishnah, also without any indication of a change of subject, returns to the topic of the previous Mishnah, or else it is an entirely new topic: before us is a pregnant consecrated animal. According to the Bartenura, in the previous Mishnah the second case was a pregnant chatas; here there is no need to say so, and it can be simply a pregnant animal, a pregnant shelamim, and the like. And once again the person seeks to define what the sanctity of the fetus will be.
This case follows the view of Rabban Shimon ben Gamliel, who holds that as long as the animal has not been born it does not take on the status of its mother. This is a dispute between Rabban Shimon ben Gamliel and the Sages, and the halachah follows the Sages, so this is not the practical halachah. In any event, in the world of Rabban Shimon ben Gamliel, when you have a pregnant offering, it is possible to designate what is in the animal's womb for a status different from that of its mother.
And this is the case before us: a person said, for the sake of discussion, "If this is a male - it shall be my olah," and what emerged is neither male nor female, but rather "yaldah tumtum ve'androginus" - it gave birth to a tumtum or an androginus:
Tumtum - the newborn has a kind of membrane or flap of skin covering its concealed organs, so that it is impossible to see whether it is male or female.
Androginos - a Greek word (the source of the English "androgynous") - the animal has both male and female organs, and is not necessarily male or female.
There is a dispute here that we have no need to enter into now: what is the status of a tumtum - the ruling is that it is a case of doubt, either male or female, and we do not know which; and what is the status of an androginos - an even more complicated discussion, whether it is male or female, both or neither. In any case, none of this makes any practical difference for our Mishnah.
Why is that? A tumtum and an androginos are unfit as an offering, and their law is that of blemished animals. Even if we were to say, for the sake of discussion, that a tumtum is male and merely has a covering of skin over it, or that an androginos has the status of a male - and there is such an opinion - it makes no difference, since they cannot be brought as offerings and one cannot consecrate a tumtum or an androginos as an offering.
Therefore it is certain that when he consecrated the offspring while it was still in its mother's womb, he had in mind, as though implicitly, that if it should turn out that it cannot be offered because it is a tumtum or an androginos, he does not wish to consecrate it. And now, once it has been born, since this was not his intention, it does not become consecrated. This is the language of the Mishnah: "Yaldah tumtum v'androginos, Rabban Shimon ben Gamliel omer: ein kedushah chalah aleihen" - the offspring does not take on the status he designated for it.
This Mishnah is explicitly according to the view of Rabban Shimon ben Gamliel, since he holds that the consecration does not take effect on the animal while it is still developing inside its mother's body by virtue of its mother's status; the status of the offspring does not follow the mother until it is actually born. But the halachah, as we have said, follows the words of the Sages: the status of the not-yet-born fetus follows its mother immediately, independent of anything he may say in the future. It emerges that this Mishnah too is not in accordance with the halachah.
In summary: In this Mishnah we learned three cases: a pregnant non-sacred animal whose owner is obligated to bring one olah, and it gave birth to two males - one of them is offered as the olah, and the second is sold to those who are obligated to bring an olah and its money is non-sacred; it gave birth to two females - one is offered as a shelamim and the other is sold to those obligated to bring a shelamim and their money is non-sacred; and it gave birth to a tumtum and an androginos - according to Rabban Shimon ben Gamliel no consecration takes effect on them, since they are not fit for an offering and the one who consecrated did not have in mind to consecrate them.