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Journal of Physiology, vol. vi, 1901. 

 Morgan, T. H., '01. — Regeneration. Columbia Univ. Biol. Series, No. 7. New 



York. 1 90 1. 

 '04. — An Analysis of the Phenomena of Organic 'Polarity.' Science, 



N. S.,vol. xx,No. 518. 

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EXPLANATION OF PLATES. 



Figs. I, 2, 3, 9, 10, II, 12, 13 were drawn with Leitz oc. 2, obj. 3, camera lucida. 



Figs. 4, 5, 6, 7, 8 were drawn with Leitz oc. 2, obj. 1-12, camera lucida. 



Figs. I to 8 are reduced one-half. 



The following lettering is used in all the figures: c, cilia; ci, cilia half developed; d, digestive region; 

 /, food in digestive region; g, muscle fibers; j, jelly gland; m, mucus; n, nuclei of parenchyma cells; 

 0, ova; p, penis; q, food among parenchyma cells; r, female reproductive opening; s, sperm; t, testis cells; 

 V, new material; *•, opening to digestive region; y, appendage. 



Plate I. 



Fig. I. Transverse section of whole worm near anterior end. (Fig. K, a — 6.) 



Fig. 2. Transverse section of whole worm near middle, through the digestive opening. (Fig. K, 

 c-d.) 



Fig. 3. Transverse section of whole worm toward posterior end, through female genital pore. 

 (Fig.K.e-/.) 



Fig. 4. Portion of dorsal margin of transverse section. 



Fig. 5. Portion of ventral margin of transverse section. 



Fig. 6. Sagittal section of anterior end after 2 days' regeneration, showing developing cilia. 



Fig. 7. Sagittal section of anterior end after 5 days' regeneration, showing accumulation of nuclei. 



Fig. 8. Sagittal section of posterior end after 5 days' regeneration, showing appearance of muscle 

 fibers. 



Plate II. 



Fig. 9. Lateral sagittal section of middle-piece after 5 days' regeneration, showing accumulation 

 of nuclei, n. 



Fig. 10. Median sagittal section of middle-piece after 2 weeks' regeneration, showing tissue with 

 the loose character of the old. (Exceptionally rapid regeneration.) 



Fig. II. Sagittal section of head-piece after 4 weeks' regeneration, showing the new digestive opening. 



Fig. 12. Sagittal section of middle-piece after 4 weeks' regeneration, showing anlage of penis and of 

 female genital pore. 



Fig. 13. Transverse section of middle-piece (4 weeks) with a "pocket," showing triangle of new 

 material, v. 



