102 JOSE F. NONIDEZ 
mosomes, so far as synapsis is concerned. But such a conclusion 
would be of very hypothetical character and is without adequate 
support in the facts observed elsewhere. 
VI. CONCLUSIONS 
1. The spermatogonial groups of Blaps lusitanica contain 
thirty-five chromosomes, thirty of which pair at synapsis, giving 
rise to fifteen bivalents in the primary spermatocytes. The 
other five chromosomes join in a group, the X-complex, during 
the early synizesis and can be traced from this stage to the 
metaphase of the first maturation division. 
2. The chromosomes of the X-complex differ in size and shape, 
three of them being much larger than two others which cannot 
be distinguished from the ordinary chromosomes in the spermato- 
gonia. The large chromosomes appear in the latter as atelomitic 
V-shaped bodies. Two of them, which appear to be homologous 
and have been termed M-chromosomes, have a submedian at- 
tachment of the spindle fibers, while the third has a subterminal 
attachment. The latter element, as shown by its behavior dur- 
ing the growth period, corresponds to the accessory or X-chromo- 
some of other forms. 
3. A resting stage intervenes between the last spermatogonial 
mitosis and the prochromosome stage. The prochromosomes 
appear as massive bodies, their number agreeing with that of 
the spermatogonial groups. 
4. Synizesis takes place when the chromatin is still in the form 
of massive prochromosomes. 
5. During the unraveling stage the M-chromosomes and small 
chromosomes of the X-complex give rise to leptotene threads, 
whereas the X-chromosome retains its dense condition. 
6. The M-chromosomes, and probably also the small chromo- 
somes of the X-complex, do not pair at synapsis, but persist 
throughout the pachytene stage as independent threads connected 
with the X-chromosome. Their relative position in the complex 
is variable. 
7. The X-complex undergoes dissociation during the anaphase 
of the first maturation mitosis. One of the M-chromosomes 
