STUDIES ON CHROMOSOMES 
67 
pale plasmosome which is considerably larger than the chromo- 
some nucleolus. This body, particularly well shown in these 
slides, is at once recognizable by its smooth contour, spheroidal 
form (sometimes double, as in fig. 11) and pale yellowish color 
after the hsematoxylin, and it forms a striking contrast to the 
intense blue-black of the chromosome-nucleolus. Nuclei in 
which all five bodies — the three small chromosomes and both 
diploid nuclei. This assumption — which is doing much to confuse the whole sub- 
ject — may accord with the facts in certain species, but certainly is not generally 
true. Much of the recent work in this field, as well as some of the earlier (e. g., that 
of McClung '00, and Sutton '00) goes to show that in many species it is only in 
the growth-period of the spermatocytes that this chromosome forms a chromosome 
nucleolus, not in the diploid nuclei of either sex. Such seems to be the case in all 
the Hemiptera that I have studied. In these animals the accessory chromosome, 
or its homologue the large idiochromosome, first assumes the nucleolus-like con- 
dition in the post-spermatogonial stages, when its origin from an elongate chromo- 
some may in some species readily be followed step by step, as I have shown in 
Lygseus ('056) and Pyrrhocoris ('096), In the spermatogonia of these animals 
this chromosome does not differ visibly in behavior from the others and cannot 
be seen in the resting nuclei. 
Several years ago, in two successive papers ('05a, '06) I described and commented 
on the interesting fact that in the female this chromosome (and its fellow, when 
present) seems in some species not to assume a nucleolus-like condition in the 
synaptic stage and early growth-period of the oocytes. Since some doubts on 
this point were raised in my own mind by the later work of Stevens ('06) and Gut- 
herz('07)I am now glad to have the very positive confirmation of my results given 
by the work of Foot and Strobell ('09) on Euschistus (one of several forms I had 
examined). This confirmation must have been made without knowledge of my 
previous work, since the latter is referred to in neither text nor literature list, and 
the supposedly new facts are made the main basis for renewed attack upon my 
general conclusions. On the other hand Buchner ('09a) has recently found in the 
synaptic or "bouquet" stage of the oocytes in Gryllus a nucleolus-like "accessory 
body" which he believes to be of the same nature as the accessory chromosome 
of the male, though its history in maturation was not followed out, nor is other 
proof of the conclusion given. 
It is of some psychological interest to find Buchner on the one hand and Foot 
and Strobell on the other disputing my conclusions regarding sex-production on 
diametrically opposing grounds, the first-named author because (as he believes) 
a chromosome-nucleolus is present in the oocyte-nucleus , the last named because it 
is absent{\). In what way either of the mutally contradictory arguments inval- 
idates or weakens my conclusions I am not yet able to perceive, nor need we here 
consider the contradiction in the data; but it is interesting to observe how each 
of the arguments goes awry by reason of the confusion regarding the chromosome- 
nucleolus, referred to above. Foot and Strobell, for example, argue that because 
