1 9i 4] SHARP— SPERMATOGENESIS IN MARSILIA 429 



3. In the third mitosis a centrosome develops at each spindle 

 pole at anaphase exactly as in the second mitosis, and during 

 telophase or later divides to two daughter centrosomes. 



* 



4. These daughter centrosomes, which may now be called 



mov 



the fourth or final mitosis. 



5. The centrosomes are at all times accompanied by extensive 

 radiations, which in the fourth mitosis give rise to the achromatic 

 figure. When the centrosome divides there is present a central 

 spindle and amphiaster as in animal cells, 



6. Before the fourth mitosis is completed the blepharoplast 

 becomes vacuolate and breaks up to a number of fragments. In 

 the spermatid these form a band which elongates spirally in close 

 union with the nucleus and bears the cilia. 



7. The evidence afforded by Marsilia, together with that 

 gained from other plants and certain animals, is believed to show 

 conclusively that the blepharoplasts of bryophytes, pteridophytes, 

 and gymnosperms are derived ontogenetically or phylogenetically 

 from centrosomes. 



The writer is greatly indebted to Professor John M. Coulter 

 for placing at his disposal the facilities of the Hull Botanical 

 Laboratory. 



University of Chicago 



LITERATURE CITED 



full 



paper on Equisetutn, cited below. 

 1. Allen, C E., Cell structure, growth, and division in the antheridia of 

 Polytrichum juniper mum Willd. Archiv fiir Zellforschung 8:121-1 88. 



pis. 6-g. 1912. 



Belajeff, W., tJb 



Zeit. 56:141-194. ph. 8, g. 1898. 



Bot. 



3. , tJber die centrosome in den spermatogenen Zellen. Ber. Deutsch. 



Bot. Gesells. 17:199-205. pi. 15. 1899. 



4. Campbell, D. H., Einige Notizen iiber die Keimung von Marsilia aegypti- 



aca. Ibid. 6:340-345. pi. 17. 1888. 



5. ■ , On the prothallium and embryo of Marsilia vestita. Proc. Cal. 



Acad. Sci. II. 3:183-205. pis. j, 4. 1892. 



