98 bulletin: museum of comparative zoology. 



different shape may behave differently in their orientation on the 

 maturation spindles. McClung has recently gone over this matter 

 in a very painstaking way, and I can agree with his conclusion that, 

 in general, the chromosomes with the spindle-fiber attachment termi- 

 nal, that is, rod-shaped chromosomes, are oriented in the first matura- 

 tion spindle so as to produce an equational division, while those wliich 

 have the spindle-fiber attachment non-terminal, that is, at the apex 

 of V-shaped cln-omosomes, become oriented so as to bring about a 

 reduction at the first division. This general rule is of course violated 

 when the pairs of rods are of unequal length, which usually (Baum- 

 gartner, '11; Payne, '12; Carothers, '13; Robertson, '15), but not 

 always (Ci, described in this paper), divide reductionally in the first 

 division. Davis ('08) sought to establish the behavior of the V- 

 shaped chromosomes of Stenobothrus as the type for the Orthoptera in 

 general. He correctly described the behavior of these chromosomes 

 in the maturations, but fell into error by attempting to make the rod- 

 shaped chromosomes conform to the same type of behavior. He also 

 failed to recognize parasynapsis. I have recently made a study of 

 the conditions in Stenobotlirus and may say that I found parasynapsis 

 for both forms of cln-omosomes, and that the V-shaped chromosomes 

 divide reductionally in the first maturation mitosis, as Davis de- 

 scribed, but that the rod-shaped chromosomes divide equationally 

 in the first division, as I found that they did in Phrynotettix. 



> 



b. Recent Work on Synapsis. 



That parasynapsis has a wide occurrence, is evident from a glance 

 at the cytological literature, especially within recent years. Gregoire 

 in his two admirable monographs ('05, '10) has reviewed most of the 

 previous literature bearing on the subject of the behavior of the 

 chromosomes in maturation, and has endeavored to find a common 

 type of behavior for both plants and animals. He says ('10, p. 384) : 

 "Dans un bon nombre d'objets animaux et vegetaux, les cineses de 

 maturation s'accomplissent suivant le type d'une prereduction hetero- 

 homeoty pique preparee par une pseudo-reduction prophasique par 

 parasyndese ou zygotenie." In this " heterohomeotypique " scheme, 

 however, Gregoire has failed to distinguish the difference in behavior 

 between the chromosomes with terminal and those with non-terminal 

 spindle-fiber attachment. Since the publication of Gregoire's later 

 monograph, a considerable number of investigators have reported 

 the existence of parasynapsis. 



