462 THE AMERICAN NATURALIST. [VOL. XXX IX. 



blepharoplast which is clearly analogous to the middle piece of 

 the animal spermatozoon. We have no evidence that such events 

 ever take place in the eggs of plants. On the contrary we know 

 that the first cleavage-spindle in the eggs of spermatophytes 

 develops without centrosomes from a mesh of fibrillae. Also 

 the blepharoplasts of the gymnosperms Cycas, Zamia, and Ginkgo 

 remain in the cytoplasm at a distance from the fusion nucleus 

 and Shaw's account of the fern, Onoclea, indicates that similar 

 conditions obtain there. We know less about the history of the 

 blepharoplasts within the egg of thallophytes where the first 

 cleavage-spindle frequently has very handsome centrospheres 

 and asters (e. g., Fucus and Dictyota). Strasburger ('97a) 

 pointed out that one of the asters of the first cleavage-spindle 

 in Fucus arose near the point where the male nucleus united 

 with the female. However, Farmer and Williams ('98) believe 

 that centrospheres of the first cleavage-spindle in Fucus are 

 formed de novo and Williams (: O4b) came to the same conclu- 

 sion for Dictyota. There are some very interesting features in 

 the comparative study that Williams (: <34b) has made on the 

 development of the first segmentation spindle in the fertilized 

 and parthenogenetic eggs of Dictyota. The spindle in the par- 

 thenogenetic egg is multipolar and develops from an intranuclear 

 kinoplasmic mesh and there are no centrospheres. But in the 

 fertilized egg a centrosphere always appears at the side of the 

 nucleus and apparently divides into two which separate until 

 they lie at opposite poles of the mature spindle. Yet Williams 

 after a very careful study concludes that this centrosphere arises 

 de novo and believes that the stimulus of fertilization enables 

 the fusion nucleus to form a centrosphere external to itself, a 

 thing which is not possible for the nucleus of the parthenogen- 

 etic egg. 



It seems then probable that the only structures of the sperm 

 that preserve their morphological entity in the fertilized eggs of 

 plants are the chromosomes. Whatever may be the relation of 

 the blepharoplast and other cytoplasmic structures as stimuli to 

 the development of the egg they cannot be regarded as fixed 

 factors in the problem of heredity. It is very probable that 

 they introduce valuable food material, perhaps important fer- 



