718 C. E. McCLUNG 



Summarizing the comparison between the rings of Hippiscus 

 and of Stenobothrus under the various headings used in the con- 

 sideration of this structure we find that there are in each case 

 (1) four chromatids derived two from the male parent and two 

 from the female parent, (2) joined so that homologous pairs are 

 united end to end and sister pairs are superimposed. (3) These 

 relations of the prophase are carried over into the metaphase where 

 (4) in Hippiscus the rings lie in the equatorial plate with sister 

 chromatids directed toward opposite poles of the spindle, while 

 in Stenobothrus although the parts of the tetrads are in the same 

 relation to each other the whole chromosomes lie extended in 

 the direction of the spindle axis with sister chromatids toward 

 the same pole. (5) In Hippiscus the sister chromatids , glide 

 away from each other and become extended in the line of the 

 archoplasmic fiber beside homologous chromatids, thus progres- 

 sively reducing the size of the ring to supply the increased length 

 of the extensions; in Stenobothrus, on the contrary the whole 

 rings separate directly into half rings or Vs. (6) The rings in 

 Hippiscus have the fiber attachment at the synaptic ends, which 

 are slightly drawn out, directly above each other, and which 

 consist each of homologous chromatids, while in Stenobothrus the 

 fiber attachment is approximately median and in each case in- 

 volves connection with sister chromatids. (7) The dyads of 

 Hippiscus in the anaphase are simple V's like all the others of the 

 complex, while the ones in Stenobothrus are double V's and unlike 

 the simple V's of the metaphase rods in the same complex. (8) 

 The results of the separation of the rings of Hippiscus is an equa- 

 tion division while in Stenobothrus it is a reductional one. 



e. The chromosomes in the second spermatocyte 



There is comparatively little difference of opinion regarding 

 the actual appearance of the chromosomes in this generation, and, 

 so far as interpretation is concerned, it is altogether dependent 

 upon the meaning attached to the first spermatocyte division. 

 While therefore extended discussion is not called for, it will be 

 convenient to keep separate the consideration of the chromosomes 

 of Hippiscus and of Stenobothrus types. 



