316 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Fig. 6. Trochophore larva, Dec. 30th, 1898, and Feb. 



3rd, 1899. 

 Figs. 7 and 8. Post-larval stages of Polycbaeta, of which 



many were taken during April, 1899. 



Plate VII. 



Fig. 1. Holothurian larva, Jan. 24th, 1899. 



Fig. 2. Echinoderm Blastosphere, at close of segmenta- 

 tion, Dec. 17th, 1898. 



Fig. 3. Gastrula stage of fig. 2, in optical section, a.c, 

 Amoeboid cells budded from the invagination. 



Fig. 4. Asterid Gastrula, Jan. 24th, 1899. 



Fig. 5. Later stage of fig. 4, showing the archenteron, ar. 



Fig. 6. Still later stage, from ventral surface. ar. } 

 archenteron, from which the enteroccelic vesi- 

 cles, v.p.d., are derived. The water vascular 

 rosette is derived, according to Metschnikoff, 

 from the left vesicle, that on right of figure. 



Fig. 7. Tornaria larva of Balcmoglossus, June 5th, 1899. 



Fig. 8. Bipinnaria larva, Feb. 23rd, 1899, from dorsal 

 surface, ce., Oesophagus ; a., Anus; hy.,'H.y- 

 dropore ; v.p.d., anterior enteroccelic vesicles. 



Figs. 9 and 10. Tornaria larvae of Balanoglossus, June 

 23rd, 1899. p.p-, Proboscis pore; p.c, Proboscis 

 cavity. Figure 10 is most probably identical 

 with the Tornaria figured by Mr. G. C. Bourne 

 (Journ. Mar. Biol. Assoc, vol. I., p. 63, PI. 

 VIII. , fig. 13). 



