138 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Among the most interesting phenomena exhibited by the monosome 
in the Orthoptera are the different forms which it assumes during the 
growth period. de Sinety (:01) first showed that in the Phasmidae 
the monosome becomes much elongated during this period and in 
some cases may be in direct connection with the spireme, while 
McClung (:02) and Otte (:06) have shown that in the Locustidae the 
monosome becomes converted into a long coiled thread. According 
to Otte this thread shortens and thickens to form a loop, which by the 
apposition of its arms becomes converted into a longitudinally double 
rod. My own observations have shown that in the Acrididae the 
monosome has a somewhat similar history, although there is con- 
siderable variation in the different subfamilies. In Steiroxys, how- 
ever, the monosome apparently remains more compact than in most 
of the Locustidae. ‘The entire history of this element is strikingly 
like that of the autosomes, but with this difference: — in the monosome 
the different autosome stages have been suppressed to a very large 
extent. It is only necessary to add that it forms a modified spireme 
and is attached to the distal pole in the same manner as the auto- 
somes, although in the monosome the spireme is found at a consider- 
ably later period. 
In the Orthoptera, as in other insects, the monosome often shows 
a distinct bipartite structure. ‘This is especially true of Stenobothrus 
and Melanoplus, where, as I have shown, during a large part of the 
growth period the monosome is composed of two distinct and dis- 
similar portions. 
McClung (:05) has described some peculiar relations between the 
autosomes and monosome in certain Orthoptera. In several species 
the monosome becomes attached to a bivalent (in Mermiria quad- 
rivalent) autosome during the prophase of the first division and this 
association persists throughout the maturation period. A similar 
condition was noticed by de Sinéty in the phasmid Leptynia. I have 
been unable to find anything of the kind in any of the Orthoptera 
studied. However, a comparison of McClung’s figures with some of 
the stages of the monosome in Stenobothrus suggest that possibly in 
some cases he has mistaken the more granular component of the 
monosome for an autosome. 
Regarding the relation of the monosome of the Orthoptera to the 
allosomes of other arthropods, it is probably directly comparable with 
the monosomes of other forms, whether they divide in the first or 
second division, since the time of division would seem to be a character 
of secondary importance. In regard to its connection with the diplo- 
