I2O MARGARET C. FERGUSON 



matic, nuclear reticula. During the dissolution of the mitotic 

 figure some of the substance of the spindle-threads probably 

 passes into the daughter-nuclei, but the greater part of the 

 fibers merge into the cytoplasmic reticulum and become indis- 

 tinguishable from it. We have here another evidence that 

 cytoplasmic and nuclear elements are but different expressions 

 of the fundamental or ground substance of the cell. When the 

 daughter-nuclei are formed they present very beautiful, monili- 

 form reticula, which later undergo changes very similar to 

 those described for the growing egg-nucleus. 



As recorded by Wilson ('96 and 'oo), Van Beneden ('83 and 

 '87) made the very interesting discovery, later confirmed by 

 Herla ('93) that the chromosomes are formed separately in the 

 sexual nuclei of Ascaris megalocephala. The differentiation 

 of the chromatic segments takes place after the entrance of the 

 sperm-nucleus into the egg but before the two nuclei have come 

 into contact. Thus the exact equivalence of the chomatic sub- 

 stance in the paternal or maternal nuclei was demonstrated. In 

 the following year, Strasburger ('88) suggested that in the com- 

 ing together of the nuclear theads lay the important point in 

 fertilization. A separating-out of the chromatic elements simi- 

 lar to that described by Van Beneden, has since been found to 

 occur during fertilization in many animals, but has not yet been 

 demonstrated as of frequent occurrence in plants. In 1891, 

 Guignard described the formation of two distinct chromatic 

 spir ernes in the copulation nucleus of Lilium Martagon, but 

 he did not figure them, and his statement seems to have been 

 overlooked by most later writers. Strasburger was able, in 

 1897, to distinguish the maternal and paternal portions of the 

 fertilized nucleus in Fucus up to the time when the spindle was 

 fully formed, and Ikeda ('02) states, regarding Trycirtis: 

 "The paternal and maternal chromatin elements of the result- 

 ing nucleus are distinguishable long after fusion." But the 

 results of more recent writers T seem to indicate that fertilization 



1 Arnoldi ('oo) in Cephalotaxus, and ('01) in Sequoia' Caldwell ('99) in 

 Lemna ; Campbell ('99) in Spharganium ; Farmer and Williams ('98) in Fucus ; 

 Guignard ('99) in Lilium j Harper ('oo) in Pyronema ; Ikeno ('98) in Cycas 

 and ('01) in Ginkgo ; Jager ('99) in Taxus ; Land ('oo) in Erigeron and Sil- 

 phium : Lotsy ('99) in Gnetum ; Merrell ('oo) in Silphium ; Mijake ('01) in Pyth- 



