This chapter was a lot like the last chapter in seeing "the common plan" in developing embryos like the gill arches, except this time it's with the three germ layers. Shubin again brings up how all creatures are really just variations on a common theme and that we all "started from a generally similar place" (99). Also "we may not look much like sea anemones and jellyfish, but the recipe that builds us is a more intricate version of the one that builds them" (115). Just as in the last, this chapter also focuses on the history of science and first understanding how things or creatures started in the first place, specifically mentioning the history of embryology and the experiments that led to discovery of the Organizer.
I was amazed at the power of the Organizer to create another embryo when grafted onto a different one, and its versatility in taking this gene from a chicken and grafting it onto an entirely different animal such as a salamander to create a twinned salamander (107).
The Hox genes also amazed me because they "establish the proportions of our bodies" (110) and that our bodies are put together so well because of them. Also the Hox genes helped me understand the organization of the body since they affect the part of the body they are located in - the head, middle, or tail segment. Shubin also talks about the symmetry of the body and how "the head is on the forward end, in the direction we typically swim or walk...'anus-forward' wouldn't work very well" (97). I found this interesting because I remember seeing the nautilus animal and how it swims "backwards" because its facing in the direction of where it has been instead of where it is going. (good thing we don't work that way) anyways, this book never fails to surprise me. i'm looking forward to reading on...
Alexis Jacalne
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