﻿iqi6] CHAMBERLAIS STAXGERIA PARADOX A 363 



the sperm is not likely to cause so deep a depression (figs. 10, n, 

 13). The ciliated band is so conspicuous and persists so long that 

 a complete series of sections' will show, even to the close of the free 

 nuclear period, whether more than one sperm has entered the egg. 

 The photomicrograph (fig. 24) shows a part of the spiral band of the 

 sperm whose nucleus has fused with that of the egg; and also 

 shows two more sperms which have passed through the neck, one 

 of which has become almost completely imbedded in the egg. 



The behavior of the chromatin during fertilization has not yet 

 been described for any cycad, but Webber (6) figured and described 

 the sperm nucleus of Zamia imbedded in the egg nucleus, and 

 Ikeno (3) found the same condition in Cycas. In Stangeria the 

 behavior is the same (fig. 9). Both nuclei, at this stage, are in the 

 resting condition. Whether they continue in this condition as 

 fusion proceeds, or break up into two groups of chromosomes, as 

 in Pinus and several other conifers, has not been observed as yet. 

 However, the structure of the first mitosis of the fertilized egg 

 indicates that the resting condition is soon followed by the forma- 

 tion of chromosomes by each of the fusing nuclei. The number of 

 chromosomes, as counted at the equatorial plate stage of the first 

 mitosis, is 12; but later free nuclear divisions and also mitoses in 

 root tips show that 24 is the diploid number; further, the mitosis 

 at the formation of the ventral canal nucleus and egg shows 12 

 chromosomes, proving that this is the haploid number. With the 

 conspicuous spiral band indicating the entrance of a sperm, parthe- 

 nogenesis is out of the question. Hutchinson's (14) recent study 

 of fertilization in Abies, from an abundance of material in critical 

 stages, which it has been my privilege to examine, furnishes an 

 explanation of this apparently haploid, but really diploid condition. 

 Hutchinson (14) finds that the spirems of the two conjugating 

 nuclei segment into chromosomes, as has been described for 

 various conifers; but, after the segmentation, the chromosomes 

 unite in pairs, just as in the prophase of the heterotypic mitosis. 

 Each pair then segments transversely and the two longitudinal 

 parts separate, so that 4 chromosomes are formed from each pair 

 and the diploid number is established. In Stangeria, 4 eggs were 

 found which showed the first mitosis, all of them in the early 



