110 



GENERAL EMBRYOLOGY 



FIG. 56. Origin of the germ cells in the Hydro-medusa, Cladonema. From 

 Wilson, "Cell," after Weismann. A. Young stage: section through the wall of 

 the manubrium. Ova developing in the ectoderm, ec; en, endoderm. B. Older 

 stage, showing ova, o, and nutritive cells, n. The ova contain small nuclei prob- 

 ably derived from ingested nutritive cells. 



FIG. 57. Diagram of the structure of the. developing ovary of the Annulate, 

 Amphitrite rubra. From Korschelt and Heider, after E. Meyer, g.dr., rudiment 

 of ovary; g.e., germinal epithelium; g.z., fully formed ova, scattering; pm., perit- 

 oneum; V.v., vas ventrale. 



