1893.] Embryology. 163 
ently results from the fusion of polar bodies; they are rudimentary 
larval organs. 
The fact that we here compare union of later generations in the 
plant with that of earlier ones in the insect or animal is perhaps made 
less objectionable by considering the state of things in the infusoria, 
where, as Maupas has shown, the final fusion takes place between 
nuclei resulting from more divisions than are employed in the 
formation of sperm and female pronucleus. 
The observations of Henking upon the number and division of the 
chromosomes in insects conflict in an important particular with the 
facts necessary to support Weismann’s theoretical explanation of the 
use of polar bodies. In his “ Amphimixis” Weismann holds that 
reduction takes place in the formation of both polar bodies, and that 
there was previously a doubling in the number of chromosomes or 
idanten to allow of greater complexity of combination of the iden or 
hypothetical hereditary units found in the chromosomes. Hinking 
denies that the second polar body is formed by reduction ; it is formed 
by an equal division. Moreover, there is no previous doubling of 
chromosomes; the apparent doubling is only a more or less pronounced 
division into parts still remaining subservient to the whole, not acquir- 
ing individuality. - 
Weismann’s views are moreover limited in that they depend upon the 
occurrence of two polar bodies, two divisions in the formation of sex- 
ual cells; whereas in plants and in infusoria, nuclei that need to copu- 
late result from more numerous divisions. 
Parthenogenesis again, as seen in hymenoptera and lepidoptera, may 
occur where two polar bodies with a smaller number of chromosomes 
are present. > l ; 
Though recognizing the strength of the evidence that heredity is 
closely associated with the chromosomes, the author thinks they are 
not unchangeable, and that at times they may be more intimately com- 
bined with the other parts of the nucleus. If the centrosomes are to 
be regarded in heredity as of like value with the chromosomes then 
we must seek in them a process of reduction before copulation. 
All present theories of fertilization and of inheritance have only a 
provisional character. 
