PLATE 9 



EXPLANATION OF FIGURES 



49 Lateral view of anterior end of an embryo which had entered the mother's 

 intestine. Drawn to show the gonads with cells in mitosis. X 730. 



50 Sagittal section through the reproductive organs showing the undif- 

 ferentiated cell mass which is to give rise to the atrium, antrum femininum and 

 oviduct; also the shell glands (gl.sh.). X 400. 



51 Sagittal section showing later stage in the development of the sexual 

 organs. Testis has become functional showing spermatogonia, primary and 

 secondary spermatocytes and mature spermatozoa. A number of the latter 

 have already reached the seminal vesicle. Not yet has a lumen been formed 

 in the antral region. X 400. 



52 Reconstruction from sections of the reproductive organs of a 0.60 mm. 

 worm which had been liberated from the mother for some time. The point of 

 view is one looking posteriorly from a point just in front of the testes. X 270. 



53 Oblique frontal section of an abnormal embryo in which the primary 

 entoderm cells, having failed to absorb yolk according to their function, still 

 remain in the center of the unusually small posterior half. The mesenchymatic 

 cells have proliferated as in normal embryos and appear in several rows. X 530. 



ant., antrum femininum 

 at., atrium commune 

 br., brain 



ent.l, primary entoderm 

 ep.t., epithelium of testis 

 esoph., esophagus 

 gl.sh., shell glands 

 gon., gonad 

 g.p., genital pore 

 0., ovary 



o.d., oviduct 



ph., pharynx musculature 



sp., spermatozoon 



spc.l, primary spermatocyte 



spc.2, secondary spermatocyte 



spg., spermatogonia 



S.V., vesiculum seminalis 



t., testis 



v.d., vas deferens 



vit., vitellarium 



556 



