190 PROCEEDINGS OF THE ACADEMY OF [Feb., 



because of the larger growth period with its much greater degree of 

 metabohsm, which is responsible for a certain inclination, curiously 

 enough still surviving in some minds, to doubt the individuality of the 

 chromosomes. The cases of peculiar interest to the student of the 

 germ cells are parthenogenetically developing eggs. All the investi- 

 gators of parthenogenesis hold that both pole bodies represent equa- 

 tional divisions, or that the second is the reductional one; and very 

 general is the opinion that the second maturation mitosis being reduc- 

 tional, and the lack of formation, or secondary retraction, of the second 

 polar body being generally associated with normal parthenogenesis, it 

 is effected that by parthenogenesis the number of chromosomes does 

 not become halved. But there is no good ground for this view, and 

 parthenogenesis with fertilization following in a subsequent generation 

 is really better explained on the idea of a prereduction. For if the first 

 maturation is reductional and the second (equational) one is eliminated, 

 the parthenogenetic egg would have one-half the normal number of 

 chromosomes ; whether this number persists through all cell genera- 

 tions of the succeeding individual remains to be determined; there is 

 some evidence that it may do so. If the half number does persist, then 

 when an egg of the following individual becomes fertilized by a sperma- 

 tozoon the normal number would be restored, instead of being multiplied 

 one and a half times. This could not be effected if the second matura- 

 tion mitosis were reductional, and the second polar body not produced. 

 And of one point we can be reasonably certain: as Sutton (1903) has 

 reasoned, there is no probability that in a reduction mitosis all the 

 paternal chromosomes pass to one daughter cell and all the maternal 

 chromosomes to another; in other words, there is no evidence that 

 half the spermatids or ovotids contain only paternal elements and half 

 only maternal. Indeed, the chance of this would decrease inversely in 

 geometrical ratio with number of chromosomes. And therefore it is a 

 wholly unfounded assumption to conclude, as some have done with 

 greater ability in the construction of hypotheses than in reasoning 

 from phenomena, that either or both pole bodies eliminate all the "male 

 chromatin" (paternal chromosomes). The great weight of evidence 

 is in favor of the view that the first maturation mitosis reduces the 

 number of chromosomes, breaks apart the univalent components of 

 the bivalent chromosomes, but does not do it in such a way as to sepa- 

 rate all the paternal from all the maternal ; and those wiio have founded 

 hypotheses on contrary premises have been w^eaving ropes of sand. 



