a 
88 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Fig. 14. Concretions from renal vesicles. x 200. 
Fig. 15. Bunch of spermatic tubules from testis. x 50. 
PLATE V. 
REFERENCE LETTERS.—ar. archenteron, at. atrial in- 
volution, aw. otolith, bc. blastocoele, bp. blastopore, 
ch. notochord, ep. epiblast, f. tail fin, fodl. follicle cell, 
hy. hypoblast, 7. intestine, m. mouth, mes. mesoblast, 
musc. muscle cells, mb. mesoblast layer, mc. mesoblast 
cell, ». nucleus of ovum, nc. neural canal. 7.e.c. neuren- 
teric canal, ».ch. notochord, 7.v. cerebral vesicle, oc. 
cerebral eye, p. protoplasm of ovum, s. spermatozoon, t.c. 
‘‘testa’’ cells of ovum. 
Fig. 1. Mature ovum and spermatozoon of Asczdia. 
Fig. 2. A segmentation stage, in section, to show blas- 
tula. 
Fig. 3. Early gastrula stage. 
Fig. 4. Later gastrula stage. 
In these and some of the other figures, the 
clear cells indicate the notochord, the hypo- 
blast cells have small circles, and the nerve 
cells are marked with oblique lines, while the 
mesoblast cells are cross hatched. 
Fig. 5. A later embryo, showing rudiments of noto- 
chord and nervous system. 
Fig. 6. Embryo showing body and tail, &c. 
Fig. 7. Transverse section of the tail of larva. 
Fig. 7a. Transverse section of the body of embryo. 
Fig. 8. Embryo ready to be hatched. 
Fig. 9. Free-swimming tailed larva. 
Fig. 10. The metamorphosis—larva attached to a stone. 
Fig. 11. Tail and nervous system of larva degenerating. 
Fig. 12. Further degeneration and metamorphosis of 
larva into 
Fig. 18. the young fixed Ascidian, 
