MCDB 4790, Class 3. Guidance Questions, Roux and Driesch papers

Please complete these before class, and bring your answers to class with you. I will ask you to turn them in at the end of the class period.

Roux 1888

Note: I know the figures are terrible—unfortunately, I cannot find a better version.

Note also that this paper is pretty long-winded; you can use the guide below to zero in on what you want to spend time reading!

Guide to the paper:

pp 4-5: outline of his ideas

pp 6-7: some background information

pp 8-9: experimental design

p 11: start of results section

skip bottom of 22-top of 25

p 25: discussion

skip pp 32-middle of 36

p 36: summary

Answer the following questions as you read:

1. What organism did Roux use in his paper? What stages of cleavage were the eggs that Roux used?

2. What did he have to say about the site of fertilization with respect to the plane of first cell division?

3. Roux described the behavior of the damaged cells according to the different structures he observed externally and internally. In this respect he described three processes that would be occurring in the treated blastomeres. Which of the processes below did Roux describe in his paper and how are they different?

a. alternative process

b. decomposition process

c. reorganization process

d. postgeneration process

e. cellularization process

4. Order from early to late the different developmental stages Roux obtained after damaging a blastomere after the first cleavage: semimorulas, semigastrulas, hemiembryones, semiblastulas

5. What did Roux find happened after the destruction of one of the first two blastomeres?

6. What did Roux conclude from his findings?

7. What was his theory of post-generation?

Driesch 1892

1. What organism did Driesch use in his paper? At which stages, and how, did he separate blastomeres?

2. What were the differences he observed between the experimental embryos and normal embryos?

3. How did Driesch name the embryos he obtained?

4. How did he describe twinning?

5. What did he have to say about the prospective potency of isolated cells?

6. Which principal did Driesch discard after his findings?

7. Why did Driesch describe the developing egg as an “harmonious equipotential system”?

General reflective questions:

1. Why are Roux and Driesch’s experiments and conclusions (despite possible inaccuracies) so important in the field of experimental embryology?

2. Were Driesch’s findings different from Roux’s because of the organism used, or because of different reasons? Explain.