G26 ZOOLOGY SECT. 



kingdom. Many of the higher flowering plants, for example, are 

 capable of being propagated by means of a cutting of the stem or 

 root, or even by a leaf. As the new plant developed from the 

 cutting gives rise to flower and fruit, the cutting must contain 

 germinal matter ; and germinal matter, must, therefore, be diffused 

 throughout the cells of such a plant. Pangenesis, unmodified, 

 would require that in such a case a large proportion of the 

 ordinary cells of the plant should receive gemmules derived from 

 all parts. 



It is a moot point whether it is possible that any in- 

 fluence (such as is pre-supposed in pangenesis) can pass from 

 the cells of the various parts of the body to the ova whether 

 there can be any communication of substance carrying with it 

 tendencies to be transmitted to the next generation. It is certain, 

 however, that an influence of a centrifugal character is exerted 

 by the sexual cells. The absence of ovaries or testes has, in 

 many cases, a marked effect on certain of the characters an 

 effect on the development and form of certain of the parts. This 

 is seen not only in higher animals (Mammals and Birds), but also 

 among some lower forms. In certain crabs, for example, the 

 presence of Sacculina, a parasitic rhizocephalan nourished at the 

 expense of the testes, which become destroyed, produces a very 

 marked alteration in some of the external features. But, while 

 this is the case, an influence exerted in the opposite direction an 

 influence transmitted from the other parts to the germ cells, has 

 not been proved, and from the nature of the case perhaps cannot 

 be directly proved. Such an influence, it is hardly necessary to 

 add, must be pre-supposed if we assent to the doctrine of the 

 inheritance of acquired characters. 



It has been already mentioned (Vol. I., p. 18) that the ovum, 

 before developing, undergoes a change termed maturation, consisting 

 in the separating from it of certain relatively small portions of its 

 substance, which are known as the polar globules. A connection 

 between this process and the phenomena of heredity has long been 

 supposed to exist, and a variety of theories have been put forward 

 aiming at an elucidation of this. It has been supposed that, in 

 order to fit it for the reception of the sperm, the ovum had to get- 

 rid of a certain part of its substance the ovum, regarded as a 

 hermaphrodite cell, had to become female by the discharge of the 

 polar globules representing the male part of the hermaphrodite 

 cell, before it was adapted to form the oosperm. This view 

 appeared to be supported by the supposed absence of polar 

 globules in the case of parthenogenetic ova, since in such instances, 

 no male element being added, the ovum would be the equivalent 

 of the oosperm without undergoing any change. But polar 

 globules are now known to occur in at least some parthenogenetic 

 ova. Other theories of maturation have been elaborated, but in 



