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THE AMERICAN NATURALIST 



[Vol. XLIV 



above all parts of the plant, protoplasmic structures are 

 most clearly brought out. 



As stated in the foregoing, fecundation manifests two 

 constellations of phenomena, the transmission of par- 

 ental characters and the power of growth and division 

 of the egg. That these two categories are in a measure 

 distinct is amply attested by phenomena of common ob- 

 servation, and by experimental evidence. That various 

 sorts of environmental stimuli, from the sting of an 

 insect to the increased osmotic power of surrounding 

 water, will impart to living cells the power of growth 

 and division is well known. The sting of an insect, for 

 example, will stimulate growth and cell division in stem 

 and leaf, which results in a gall ; the presence of a pollen 

 tube will induce an ovule to grow to mature size though 

 no embryo develops within it. In these and in other 

 similar cases, too numerous to mention, we have merely 

 responses to external stimuli, for doubtless the pollen 

 tube may act as an external stimulus, and no one will 

 contend that these phenomena have to do with the trans- 

 mission of parental characters. From our standpoint 

 the phenomenon of artificial parthenogenesis merits 

 especial attention. When the egg-cells of certain ma Hue 

 animals are stimulated to develop by external agencies 

 of whatever sort, it has become fashionable to speak of 

 the fact as fertilization, but whatever meaning be put 

 into the word fertilization, the phenomenon in question 

 is not fecundation or sexual reproduction. Even though 

 in every case the most sanguine expectations of the ex- 

 perimenter be realized, namely, the development into an 

 adult of an egg thus stimulated, the process would teach 

 us nothing more about sexual reproduction and the 

 transmission of parental characters than ordinary par- 

 thenogenesis. The fact that a larva having purely 

 maternal characters will develop from a sea-urchin egg 

 with which the sperm of a starfish had united, does not 

 show that hereditary characters are handed down by the 

 cytoplasm. If, on the contrary, the gastrula, showing 

 only maternal characters, which Godlewski ( '06) reared 



