CHROMOSOMKS IN TflR SPERM ATOCENESIS OF THE HEMIPTERA HETEROPTERA. 127 



autosomes (Figs. 215-219, all of them shown in Fig. 217), which are much larger than 

 any of the 4 diplosomes ; they are at first of very diverse forms, inasmuch as each may 

 have its univalent components meeting at an angle, or placed side by side, or more or 

 less twisted around each other ; the longitudinal split may be narrow for its whole 

 length, or may be widest at the middle. These generally condense so that in each the 

 univalent components come to lie in one line and the longitudinal s})lit becomes 

 obscured (Fig. 219). 



On pole views of the monaster stage (Figs. 221, 222) are seen always 9 elements. 

 The 6 largest are tlie bivalent autosomes (those that are not lettered), the smallest one, 

 which is usuall}'- central in position, is l)ivak'nt being the pair of small diplosomes 

 (Di. 1, (li. 1) the components of which ma}" lie one above the other or else side by 

 side. The 2 remaining elements are those marked Di. 2, di. 3 ; they are unequal in 

 volume and are placed apart from each other upon the periphery of the chromosomal 

 plate ; these are the elements of the larger diplosome pair, each of them univalent. 

 A lateral view of the spindle (Fig. 220) shows the small bivalent diplosome {Di. 1, di. 

 1), the separated univalent diplosomes of the larger pair {Di. 2, di. 2), and 3 of the 6 

 autosomes. The 6 autosomes and the small bivalent diplosome divide reductionally 

 as can be told from their position within the spindle ; but each large diplosome by 

 dividing separately undergoes an equation division ; each second spermatocyte receives, 

 accordingly, 6 univalent autosomes, one whole univalent component of the smaller 

 diplosome pair, and a half of each component of the larger diplosome pair. 



Second Maturation Division. — Pole views of the equatorial plate (Fig. 224) show 

 only 8 elements, and not 9 as in the preceding mitosis. The six largest are the auto- 

 somes, and the very smallest is clearly the small diplosome {Di. 1). The element 

 lettered di. 2 must therefore be composed of two elements, in order to account 

 for the apparent reduction in nunil)er in the second spermatocyte ; and it is in- 

 deed bivalent, the composite of the components of the larger diplosome pair, for 

 on lateral aspect of the spindle (Fig. 223) this chromosome is found to be com- 

 posed of 2 Ijodies of dissimilar volumes placed end to end {Di. 2, di. 2), and we 

 found that the dijilosomes of the larger pair were characterized by this dissimilar- 

 ity in volume. From the position of all these elements in the spindle it becomes 

 evident that all the autosomes divide again, so equationally, and that the small diplo- 

 some {Di. 1) does the same ; but that the bivalent larger diplosome divides i-eduction- 

 ally in that its larger component passes into one spermatid and its smaller one 

 into another. Only one good pole view of a spermatid was found (Fig. 225) ; this 

 showed 7 elements which from their size are to be considered the 6 autosomes and the 

 smaller component of the larger diplosome pair, while the element of the smaller di2> 



