EXPLANATION OF PLATE IIL 



Fig. 1. Polydora (Leucodore) cUiata, with ova, from a photomicrograph, 

 highly magnified. Original. 



,, 2. Young larvio of Polydora fi-om a photomicrograph, taken shortly- 

 after its escape from the ova-sac, highly magnified. Original. 



„ 3 & 4. Older stages, from a photomicrograph, highly magnified. 

 Original. 



„ 5 to 9. Somewhat more advanced, after Prof. A. Agassiz. 



J, 10. Egg-cases of Polydora, attached to the side of the membranous 

 tube, X 7 diameters. 



