5i8 The Ohio Naturalist [Vol. XV, No. 7, 



SUMMARY. 



The normal hereditary mechanism then of the chromosomes 

 acts as follows: 



1. The chromosomes normally function as individuals and are 

 segregated as such at each karyokinesis. 



2. The chromosomes do not conjugate or fuse, nor does their 

 material mix in the fertilization stage; but each chromosome is 

 carried thru the zygote stage of the organism as a definite indi- 

 vidual. 



3. In the reduction division, the chromosomes show them- 

 selves to be definitely paired; and the 2x number of the zygotic 

 individual represents two definite sets or complements of chromo- 

 somes, each one of the one set having its corresponding synaptic 

 mate in the other. A specific attraction develops between each 

 pair of synaptic mates during the prophases of reduction resulting 

 in an end to end fusion in pairs and a subsequent folding side by 

 side, so that a bivalent chromosome represents synaptic univalents 

 fused longitudinally at least in the ordinary elongated types of 

 chromosomes. 



4. The segregation of the univalents during reduction is 

 according to the law of chance; therefore, each daughter cell 

 receives a full (x) complement of univalents, some of the set being 

 descendants of those brought into the zygote by the parent egg 

 and some by the sperm. 



5. These processes are in harmony with the observed phenom- 

 ena of Mendelian heredity. 



CORRECTION 



The list of Insect Galls of Cedar Point (Ohio Naturalist, 

 December, 1914) is in error as follows: 



P. 381 — Andricus futilis O. S. should doubtless be Dryophanta 

 papula Bassett. 



P. 382 — Holcaspis globulus Fitch was found on Quercus 

 macrocarpa instead of Q. imbricaria. 



I am indebted to Mr. L. H. Weld of Evanston, 111., for these 

 corrections. 



Paul B. Sears. 



