A Cytological Study of Artificial Parthenogenesis etc. 163 



Fig. 1. Unfertilized ovum. Std. ARNOLD. 



Fig. 2. Ovum, 15 minutes after treatment, for 120 sees., with a solution of 



butyric acid, showing the appearance of a clear perinuclear zone (p.*.), 



surrounded by chromatic granules (ch.gr.}. Std. HEID. 

 Fig. 3. Ovum 5. minutes after transference from hypertonic salt solution to normal 



sea water (treatment undergone: butyric acid 2 mins., water 20 mins., hyper- 

 tonic salt solution 45 mins., water 5 mins.), showing the appearance of the 



perinuclear zone. Std. MALL. 



Fig. 4. Appearance of cleavage aster 30 mins. after transference from hyper- 

 tonic solution. (But. 2 mins., water 20 mins., hyper. 45 mins., water 30 mins.) 



Std. HEID. 

 Fig. 5. Polar view of equatorial plate showing 18 chromosomes. (But. 2 mins., 



water 20 mins., hyper. 45 mins., water 50 mins.) Std. ARNOLD. 

 Fig. 6. Lateral view of nuclear spindle, drawn from same slide as Fig. 5. 

 Fig. 7. Anaphase of first division of egg. (But. 2 mins., water 20 mins., hyper. 



45 mins, water 80 mins.) Std. MALL. 

 Fig. 8. Completion of first division. (But. 2 mins., water 20 mins., hyper. 



45 mins., water 100 mins.) Std. HEID. 

 Fig. 9. Anaphase of second division. Std. ARNOLD. 

 Fig. 10. 8-cell stage of chemically fertilized egg showing stages in aggregation 



of the chromatin and development of the cleavage aster. Std. ARNOLD. 

 Fig. 11. Parthenogenetic blastula, 24 hrs. old, one cell showing equatorial plate 



containing 18 chromosomes. Std. HEID. 

 Fig. 12. Normally fertilized embryo, 4- to 8-cell stage; showing equatorial 



plate containing 36 chromosomes. Std. HEID. 

 Fig. 13. Ovum 3 hours after treatment for 2 mins. with butyric acid (Temp. 



16 C.), showing the cytolytic nature of degeneration. Std. MALL. 

 Fig. 14. Large monaster developed 2y 2 hours after treatment with butyric acid 



alone. Std. HEID. 

 Fig. 15. Abnormal embryo showing the development of cytasters (cyt.) 60 mins. 



after chemical fertilization. (But. 2 mins., water 20 mins., hyper. 50 mins., 



water 60 mins.) Std. HEID. 



11* 



