124 EXPLANATION OV PLATES. 



Fig. 9. Section of test of Ascidia, to show "vessels" and "bladder- 

 cells," magnified. 



Fig. 10. Diagram showing Ascidian from left side, in correct morpho- 

 logical position for comparison with Vertebrates,, to illustrate 

 the course of the circulation, &c. 



PLATE C. 



Fig. 1. Ovum and spermatozoon. 



Fig. 2. Segmentation stage of embryo. 



Fig. 3. Early gastrula stage. 



Fig. 4. Later gastrula stage. 



Fig. 5. Embryo showing notochord and neural canal. 



Fig. 6. Later embryo showing body and tail, &c. 



Fig. 7. Transverse section of tail of larva. 



Fig. 8. A young tailed larva. 



Fig. 9. An older tailed larva. 



Fig. 10. Larva attaching itself to a stone. 



Fig. 11. Tail, &c., of larva degenerating. 



Fig. 12. Metamorphosis of larva into 



Fig. 13. Young Ascidian. 



PLATE CLAV. I. 



Fig. 1. Large colony of Stereoclavella australis, Hurdman, nat. size. 



Fig. 2. Colony cut in section to show stolonial tubes and buds, nat. 



size. 



Fig. 3. Group of Ascidiozooids, nat. size. 



Fig. 4. Ascidiozooid removed from test, right side ; enlarged. 



Fig. 5. The same, left side ; enlarged. 



Fig. 6. Part of surface of test showing spines. S. -J-. 



Fig. 7. Section through deeper part of test. S. f. 



Fig. 8. Part of mantle. S. 1. 



Fig. 9. Small part of branchial sac. S. 1. 



Fig. 10. Dorsal edge of branchial sac showing languets. S. 1. 



Fig. 11. Section through basal part of test showing vessels and buds. 

 S. 1. 



PLATE CLAV. II. 



Fig. 1. Podoclai'dla mcridiondlis, n. sp., nat. size. 



Fig. 2. Body removed from test showing thorax and abdomen, nat. size, 



