Plate II. 





Fig. 20. — Left anterior portion of a young Lingula of 5 mm. shell length, 



showing the otocyst. Unstained clarified preparation, x 80. 

 Fig. 21. — Sagittal section through a young Lingula of 6.5 mm. shell 



length. Acetic-sublimate preparation, x 80. Iv. liver lobule. 

 Fig. 22. — Otocyst of the same section as that drawn in Fig. 21. x 500. 



oil. otoliths. 

 Fig. 23. — Portion of sagittal section through a young Lingula of 6.5 mm. 



shell length, showing the heart, x 380. 

 Fig. 24. — Portion of sagittal section through a young Lingula of 7.5 mm. 



shell length, showing the heart and the muscle running below it. 

 x 729 (immers). 

 Fig. 25. — Spermatozoa, from living material, x 500. 

 Fig. 26. — Portion of transverse section through young Lingula of ').') mm. 



shell length, showing the young ova in the ileo-parietal band. A 



portion of the nephridium is also represented, x 729 (immers). 

 Fig. 27. — Section through the ovary of the adult, x 729 (immers). 

 Fig. 28. — Full grown ovarian ovum from the above section, x 490. 

 Fig. 29. — Three nuclei of ovarian ova, each with a principal nucleolus and 



accessory nucleoli. 

 Fig. 30. — Section through the ovary of an old individual killed late in the 



autumn, x 490. 



