OKLAHOMA ACADEMY OF SCIENCE 57 



In snails the inverse type of si'mmetry is termed sinistral and the 

 normal dextral. The internal organs of animals, including man, 

 may rarely show a complete reversal such as heart, liver, and the 

 like. Conklin M'ith reference to the question of cytoplasm and 

 chromosomes writes, "There is evidence that the chromosomes of 

 the egg and sperm are the seat of the differential factors or deter- 

 miners for Mendelian characters, while the general polarity, sym- 

 metry, and pattern of the embryo are determined by the cytoplasm 

 of the egg," (Conklin, E. C, Heredity and Environment, 1916, 2nd 

 edition, Princeton Press). Loeb, relative to a similar question 

 writes, "The facts of experimental embryology strongly indicate the 

 possibility that the cytoplasm of the egg is the future embryo (in 

 the rough) and that the Mendelian factors only impress the indi- 

 vidual (and variety) characters upon this rough block" (Loeb, J., 

 The Organism as a Whole, 1916, G. P. Putman's Sons.) 



The experimental embryologist has maintained, since develop- 

 ment of an egg-nucleus plus some of its cytoplasm may be stimu- 

 lated with the aid of the sperm and, since the sperm alone can not 

 be made to develop by any such manner except with the cytoplasm 

 of the egg, that the cytoplasm of the egg is essential for develop- 

 ment. These are in general the evidences against the chromosome 

 mechanism as being the determiners of developmnt. In contrast 

 to this the writer wishes to set his own results with Bruchus, and 

 to list from other sources, evidences in favor of the chromosome 

 mechanism. 



The first fact to which I wish to call your attention is that the 

 nucleus plus cytoplasm is necessary for any development. The 

 cytoplasm alone unless it has a male or female nucleus, can not 

 be made to develop. The only conclusion possible from such an 

 argument is that chromosomes and cytoplasm are essential. Cyto- 

 plasm may be necessary as a food supply in furnishing possibly, 

 the liberated enzymes given off by the genes, which may be the 

 essential stimulus for development;. 



Another type of evidence is used by Loeb as leading to the 

 belief that cytoplasm determines polarity, while the Mendelian 

 factors simply shape structures. By puncturing the eggs of frogs 

 with a fine needle, Loeb produced seven parthenogenetic adult 

 male frogs. These males were not unlike the normal males pro- 

 duced by the stimulus of spermatozoon. Bilateral symmetry was 

 evident ; this however, is no disproof for the chromosome pair, 

 one chromosome, could carry all genes necessary. Further, the 

 fact that these frogs were all males having only one x-chromosome 

 is also added proof of the determination of symmetry by the chrom- 



