SYNAPSIS AND CHROMOSOME ORGANIZATION 493 



and furthermore, they appear to be joined to single chromomeres 

 in three of the four illustrations. In both cells, that end of the 

 chromosome, near which the appendages are attached, is united 

 with the end of another chromosome, the opposite ends being 

 free in each case. In figure 23 the burdened ends of these two 

 chromosomes are joined together, the appendages are in contact 

 and, so far as could be determined, may possibly be fused at 

 the point of contact. It will be noted that the chromomere to 

 which the appendages are attached appears to be in about the 

 same position with reference to the end of the segment in both 

 cells. 



A study of still earlier stages to determine whether these ap- 

 pendages may be double, that is, one for each conjugant, was 

 not made. In the stages shown on plate 2 the bunches of gran- 

 ules were so disposed as to make it impossible to determine 

 whether or not their attachments were restricted to one pair of 

 chromatids. Structures which were interpreted as representing 

 these appendages were seen in the nucleus from which figure 21 

 was made but were not drawn because to have done so would 

 have confused the other features which were to be emphasized. 



A third point on the subject of organization is the occurrence 

 of the transverse clefts or constrictions at the points of spindle- 

 fiber attachment in the atelomitic chromosomes. These clefts 

 have been described in another connection so that it will be 

 unnecessary to repeat' a description of them. 



In passing, it may be noted that the distribution of the 

 accessory chromosome with reference to the members of the 

 heteromorphic pairs follows the law of chance, as discovered by 

 Carothers ('17). (See chromosomes 1, 3, and 8, plate 2.) 



g. Summary. In this individual of Trimerotropis the fol- 

 lowing conditions have been found: 



1. The reduced number in the first spermatocyte is twelve 

 (plus one supernumerary). The complex consists of five pairs 

 of telomitic chromosomes, four pairs of atelomitic chromo- 

 somes, two heteromorphic pairs, and the atelomitic accessory 

 besides the supernumerary. These facts were all previously 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 2 



