140 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
without attempting any specific statement. McClung (:01), Stevens 
(:05°, :06°) and Wilson (:06) have pointed out the possible signifi- 
cance of the allosomes in sex determination, so that it is unnecessary 
to take up this subject, especially since in the present state of our 
knowledge it can only lead to fruitless theorizing. I think it must be 
conceded that we have at present no satisfactory explanation of either 
the origin or function of the allosomes, and until we know more about 
these interesting elements, especially during oégenesis and fertilization 
it is idle to speculate further on the subject. 
6. THe INDIVIDUALITY OF THE CHROMOSOMES. " 
The theory of the individuality of the chromosomes, which was 
first formulated by Rabl (85) and later ardently advocated by Boveri, 
has in recent years received strong support, especially from writers 
on insect spermatogenesis. ‘The constant recurrence in successive 
generations of the autosome pairs, which are so clearly marked in 
these forms, is very difficult to explain on any other view. When 
we consider that each species is characterized by a fixed number of 
symmetrically paired autosomes which possess definite form and size 
relations, it is almost impossible to escape the conclusion that we are 
dealing with distinct morphological entities. This is perhaps nowhere 
shown to better advantage than in the aphids, where Stevens (:05, :06, 
p. 15) has shown that: “In every one of the twenty-four species 
examined some or all of the chromosomes possess characteristics which 
distinguish them from their fellows, and these peculiarities persist 
throughout all the generations. In every species where it has been 
possible to study and compare the germ cells of the parthenogenetic 
and sexual generations the single series of the maturating sexual 
germ cells has been found to be exactly duplicated in the double 
series of the parthenogenetic egg, the segmenting winter egg and 
the spermatocytes before reduction.” 
The Orthoptera also furnish strong evidence for the individuality 
of the chromosomes especially in the case of Stenobothrus and Stei- 
roxys, where, as previously described, the autosomes vary in their 
method of attachment to the mantle fibers. In Stenobothrus five of 
the eight autosome pairs always have the mantle fibers attached to 
one end. In two of the remaining three pairs the mantle fibers are 
inserted nearer one end than the other, while in the third pair the 
insertion is at the center. In Steiroxys the insertion is at the end in 
all except one pair of autosomes, while in that pair it is always near the 
middle. 
