Чем различаются следующие стадии эмбрионального развития: бластула, гаструла, нейрула?

Бластула-однослойный зародыш Гауструла-2ухслойный Нейрула-3ехслойный

1.i am betty.i am twelve.i am in fifth form.i have a lot of interesting subjects at school. 2.i am from dmitrov.it`s a small town in russia.i am in sixth form.at school we study english and french. 3.are you in a fourth form? - no,i`m not.i`m in fifth form. 4. a school year in russia starts on a first of september. 5.do you enjoy p.e,? 6.can you gather mushrooms in summer? 7.when do you go to a disco? 8.you can see different toys there. 9.do you play different games at home? 10.do you go to a stadium after school?

1. i am betty. i am twelve. i am in the fifth from. i have a lot of interesting subjects at school.2. i am from dmitrov. it's a small town in  russia. i am in the sixth form. at school we study english and french.3. are you in the fourth form? — no, i'm not. i'm in the fifth form.4. a school year in russia starts on the first of september.5. do you enjoy p.e.? 6. can you gather mushrooms in summer? 7. when do you go to the disco? 8. you can see different toys there.9. do you play different games at home? 10. do you go to a stadium after school?