578 



THE AMERICAN NATURALIST. [Xo 



XXXV I II. 



material occupied a restricted region in the middle of the spiral 

 structure. This was the first of a series of invest igat ions which 

 have given especial attention to cytoplasmic activities during 

 spermatogenesis and placed the entire subject in a new light. 



The year 1897 brought forth almost simultaneously three short 

 papers by Webber ('97a, '97b, '97c) and Belajeff ('97a, '97b, 

 '97c) respectively. Webber had studied the development of the 

 motile sperms of Zamia and Ginko, Belajeff certain forms of the 

 Filicineae and Equisetineae. These were of the nature of pre- 

 liminary^ announcements and both authors published later more 

 detailed descriptions and discussions. The discoveries of motile 

 sperms in Ginko by Hirase and of Cycas by Ikeno were 

 announced in several short papers during the years 1896 and 

 '97 but without descriptions of their development. This litera- 

 ture together with later papers of Ikeno, Shaw, Belajeff, Hirase, 

 and Fujii is reviewed in Webber's last contribution (:oi) and 

 also in Strasburger's discussion of " Cilienbildner " (: 00, p. 177) 

 to which the reader is referred for the most complete treatments 

 of spermatogenesis in plants yet published. 



The cycads and Ginko are the most favorable subjects known 

 for studies in spermatogenesis. Detailed accounts of the cycads 

 are given by Ikeno ('98b) for Cycas and by Webber (:oi) for 

 Zamia, these forms agreeing with one another in all essentials. 

 Two sperms are developed from the daughter cells (spermatids) 

 following the division of the so-called body cell in the pollen 

 tube. The process really begins in the body cell with the 

 appearance of the blepharoplasts. Their development has been 

 followed with especial attention in Zamia. They are formed 

 de novo in the cytoplasm at some distance from the nucleus and 

 while the latter is in the resting condition. They appear inde- 

 pendently of one another, generally on opposite sides of the 

 nucleus but sometimes much nearer together (Fig. loa). Each 

 is a large deeply staining body with numerous radiations 

 extending into the cytoplasm. The blepharoplasts then increase 

 m size and, movmg farther away from the nucleus, take positions 

 ^ exactly opposite to one another. The nucleus of the body cell 

 now divides, its spindle being clearly intranuclear (Fig. 5 d) and 

 consequently holding no visible relation to the blepharoplasts 



