THE GAMETES IN PLANTS AND ANIMALS 333 



a presumption in favor of a similar origin in animals, and the pur- 

 pose of the present section is to show that the facts themselves, 

 when correctly analyzed, point to the same conclusion. The 

 assumption of the existence of supplementary germ plasm, i.e., 

 of portions of germ plasm in the nuclei of all or certain somatic cells 

 or tissues, not only finds no support in the data of observation and 

 experiment, but deprives the germ-plasm hypothesis of all scientific 

 value. It is undoubtedly true that the more highly specialized 

 cells of an organism, be it animal or plant, do not so readily undergo 

 dedifferentiation and redifferentiation under altered correlative 

 conditions and so do not so readily give rise to germ cells or other 

 parts as do the less highly specialized cells; in fact, many cells, 

 especially in the higher forms, are probably incapable of such 

 change, but this does not constitute adequate grounds for the belief 

 that germ plasm and soma are independent entities. 



Summing up, it appears that the facts afford no adequate 

 grounds for regarding the germ cells as anything else than an 

 integral part of the organism specialized in a certain direction like 

 other parts. But in spite of the complete absence of any trace of 

 early segregation of germ cells in many organisms, in spite of the 

 fact that the egg cytoplasm, not the nucleus, is apparently respon- 

 sible in most if not in all cases of early segregation, in spite of our 

 ignorance in many cases whether the so-called primitive germ cells 

 really give rise only to gametes, and, finally, in spite of the remark- 

 able conception of the organic world to which the germ-plasm 

 theory leads us in spite of all these difficulties, the view that these 

 processess of early specialization in the egg constitute a spatial 

 morphological segregation of the independent germ plasm from the 

 body or soma still finds supporters, as is evident from the most 

 recent consideration of the subject by Hegner ('14^). 



THE MORPHOLOGICAL CONDITION OF THE GAMETES 



Minot ('08) has maintained on morphological grounds that the 

 animal egg is an old cell approaching death, but has not, so far as I 

 am aware, expressed any opinion regarding the condition of the 

 spermatozoon, although, according to his theory that increase in 

 the proportion of cytoplasm to nuclear substance is a fundamental 



