120 bulletin: museum of comparative zoology. 



somes. These results have been confirmed in the case of the sperma- 

 togonia by Montgomery (:06), who has investigated a large number 

 of Hemiptera from this standpoint. Montgomery also noted that the 

 members of each pair are usually closely associated during mitosis. 

 In this paper he goes further than any of the preceding authors and 

 claims that while the autosomes are evidently paired, yet the compo- 

 nents of each pair are never of exactly the same size. This he believes 

 to be due to the fact that the chromosomes derived from the female 

 parent are always slightly larger then those from the male parent. 

 That it is possible to distinguish such slight differences in size, appears 

 to me in the highest degree improbable. Even though exactly alike, 

 two chromosomes would rarely appear of precisely the same size, owing 

 to slight variations in fixation, or staining, or to different degrees of 

 foreshortening, etc. It is indeed probable that the components of a 

 pair often differ slightly in form, volume, etc., yet there seems to be no 

 good reason for believing that these slight differences persist from gen- 

 eration to generation. During the resting stage each chromosome 

 becomes broken up into fine granules, which double in volume before 

 the next division, and it would seem to be asking too much of the 

 theory of the individuality of the chromosomes to expect each chromo- 

 some to be reconstituted with exactly the same form and volume as in 

 the preceding division. Moreover, Montgomery's reason for consid- 

 ering that the smaller chromosomes are always derived from the male 

 parent does not seem to be well foimded. It is based entirely on 

 analogy with the diplosomes, where it is probable that in the case of 

 the male germ cells the smaller diplosome is derived from the male 

 parent. Montgomery apparently forgets that in the female the dip- 

 losomes are of equal size although one is of paternal, the other of 

 maternal origin. 



Otte (:06) has found that in the spermatogonia of Locusta the 

 •autosomes are paired, and Zweiger (:06) has shown that the same is 

 probably true of Forficula. 



In other groups similar results have been obtained by a number of 

 recent writers, although in many cases the individual pairs are not as 

 marked as in the insects. Among the arachnids the autosomes of 

 Lycosa have been shown to be paired by Montgomery (:05) and those 

 of Epeira by Berry (:06). In the worms, Montgomery has found 

 that in the first cleavage spindle of Ascaris megalocephala two of the 

 four autosomes are somewhat larger than the others. A. und K. E. 

 Schreiner (:06) found that in Tomopteris there are eighteen auto- 

 somes in the spermatogonia, two being considerably shorter than the 



