1 . The chorion extend to one-fifth the diameter of 

 the ovum and becomes oval . 2 . At this time a light 

 fluid, similar to albumin, discharges from the ovum. 

 3. The yolk loses its spherical form, its mass 

 loosens, and the contours become wrinkled. 4. The 

 embryonic vesicle and the embryonic spot disappear. 

 5. The upper layers of the yolk lose their reddish 

 coloration. 6. In too many cases separate yolk 

 cells are separated from the other mass of the 

 yolk and give origin to the parasitic creatures. 20 



7 . The ovum is divided by a fissure into two globules . 



8. The division process continues regularly. 



9. The yolk acquires the form of a mulberry. 



10. A bubble of air leaves the yolk (?) . 11. The 

 surface of the yolk becomes granular. 12. First 

 establishment of the embryo. The yolk acquires an 

 elongated form, and then the form of a roughly 

 outlined triangle. 13. The distinct appearance of 

 the animal system and the cutaneous system. The 

 configuration of the embryo. 14. Twisting of the 

 anterior part of the embryo is noted (future 

 organs of movement) . 15. On the wide anterior area 

 folds appear, from which two lateral round growths 

 are gradually formed. The growths are transformed 

 into lobes and between them a third growth, the 

 foot, appears. 17. Beginning of the formation of 

 mantle and concha. 18. On the lobes the cilia grow. 

 19. The first movement of the embryo. On the foot 

 the vibrating cilia appear. 21. The lobes of the 

 sail become disc-shaped. The rotatory movement of 

 the embryo. 22. Cells sharing in the formation of 

 mantle are dissolved and disappear. 23. The concha 

 significantly enlarges. 24. The isolated cellular 

 rows indicate the formation of the attached muscles . 



25. The formation of the internal organs, among 

 which the intestine is distinctly differentiated. 



26 . The liver and other glandular bodies are clearly 

 seen. The anus and ganglia. 27. The cells forming 



20. Nordmann gave this parasite the name Cosmella hydrachnoides 

 and suggested the possibility of its origin from particles 

 of the yolk of Terg-ipes. 



555 



