GR’s letter is a gold-mine.

Pleased to have Pierre Gratiolet’s comment on the embryology of greatly modified organs

and GR’s valuable cases of analogous variation.

Doubts craniologists, but recounts his father’s opinion that the shape of CD’s head was altered when he returned from the Beagle.

The embryology of the vertebrate nervous system may be an exception to the law of inheritance at corresponding ages.