Section 23. the Formation of the Respiratory Slits Is Complicated, and

difficult to describe, but, since investigators have still to render its meaning apparent, it need not detain the elementary student.*

* See Balfour's Embryology, Volume 2, and Quarterly Journal of Microscopical Science March, 1891.

Questions on Amphioxus

1. Draw diagrams, with the parts named, of the alimentary canal of (a) amphioxus, (b) any craniate; (c) indicate very shortly the principal structural differences between the two.

2. Describe, with a diagram, the circulation of amphioxus. Compare it with that of the craniata.

3. Draw from memory transverse sections, of amphioxus (a) in the oral region, (b) through the pharynx, (c) just anterior, and (d) just posterior to atrial pore.

4. Describe fully the coelom of amphioxus, and compare it with that of the frog in regard to (a) development, (b) its relation to other organs in the adult.

5. Compare the atrial cavity and coelom of amphioxus. To what series of cavities in the frog are the metapleural canals to be compared?

6. Describe the notochord of amphioxus, and point out its differences from the vertebrate notochord.

7. Describe, with diagrams, the nervous system of amphioxus, and compare its nervous axis, in detail, with that of a vertebrate.

8. Compare the genital organs of amphioxus with those of a higher vertebrate.

9. What structures have been regarded, as renal organs in amphioxus?

10. What is a gastrula? With what lower type has the gastrula been compared? Discuss the comparison.

-Development_

The Development of the Frog