494 THE SPECIFIC CONSTITUTION OF PROTOPLASM. 



the cell-nucleus was held to be correct. The fact of the constancy of species 

 from generation to generation was therefore referred, especially, to the specific 

 constitution of the cell-nucleus. Since the nucleus plays such an important part 

 in the process of fertilization, which precedes the inception of the new individual 

 in sexual reproduction, the hypothesis was put forward that the constancy of 

 form in the offspring, or, in other words, the transmission of form, depends upon 

 the specific constitution of the nuclei taking part in this process. Nor would 

 this hypothesis be open to objection had not recent investigations shown it to 

 be extremely probable that portions of the male cell other than the nucleus assist 

 at this process. If, as it appears, more than the mere nucleus passes over from 

 the pollen -tube at fertilization (cf. p. 417), how can we certainly allege that (to 

 take a definite case) all the properties which the young plant inherits from its 

 male parent are transmitted through the medium of the nucleus? If it be true 

 that a certain portion of the cell-protoplasm takes part in this act, it must be 

 proved that it plays only a subordinate part in the process (e.g. a nutritive function) 

 before we can attribute to the nucleus the part of sole carrier of transmitted 

 properties. 



To the proposition that new individuals with the unaltered properties and 

 characteristics of the species can only spring from the protoplasm of this nucleus, 

 we cannot assent. Thousands of plant-species reproduce asexually in unaltered 

 form by spores and other offshoots. As already stated so often, every young cell 

 of a plant may be the starting-point of an offshoot or brood-body, and so may 

 lead to the beginning of a new individual; and an individual produced in this 

 way bears all the characteristics of the parent plant which produced the offshoot. 

 It might even be asserted that the features of the species are more certainly 

 inherited in the case of reproduction by offshoots and brood-bodies than in sexual 

 reproduction, and in a subsequent chapter it will be shown that it is sexual repro- 

 duction alone which affords the possibility of posterity with altered characteristics. 



The view that the part surrounding the nucleus of a protoplast, the cell-proto- 

 plasm or cytoplasm, has no formative importance is not borne out by the evidence 

 of investigations into the origin of the so-called galls, which we shall discuss in 

 detail later, nor by our knowledge of hybrids. On the contrary, hybridization 

 causes not only an alteration of form in the new individual arising from the 

 germ-nucleus, but also an alteration in the form of the tissue in the region of 

 the ovule exclusively influenced by the cytoplasm, so that the effect of hybridi- 

 zation can be recognized even in the fruit which arises from the ovary. Every 

 influence on the cell-nucleus must be transmitted through the cytoplasm. But 

 it would be much more difficult to imagine that the cytoplasm remains quite 

 indifferent to this transference than that it also experiences a change identical 

 with or similar to that undergone by the cell-nucleus. Fortified by these con- 

 siderations, we may then assume (1) that all protoplasts which we know are able 

 to form the starting-points of new individuals have the capacity of transmitting 

 the external form of the species unaltered to the offspring, and (2) not only a part 



