No. 419.] ONISCUS ASELLUS LINN. 925 
III. SUMMARY. 
The main results of this study may be briefly summarized 
as follows : 
1. The spermatogonic chromosomes are joined together in 
pairs in the synapsis to form sixteen bivalent chromosomes. 
2. A longitudinal splitting of the thread takes place at t 
stage. 
3. The distinctness maintained by the chromosomes up to 
the formation of the nuclear network of the resting spermat- 
ocyte and the manner of origin of the spermatocytic chromo- 
somes from it lends support to the theory of their individuality 
in the resting nucleus. 
4. In the structure and mode of orig 
mosomes two main types may be distinguished : (a) the com- 
ponent chromosomes lie end to end, or (b) they lie side by side. 
5. Inasmuch as univalent chromosomes are separated, the 
first maturation division is reducing. 
6. Sphere substance (idiozome) is not observable, except for 
a short time during the prophases of the first spermatocyte. 
7. The nucleolus of the spermatogonia disappears 7 
after dissolution of the nuclear membrane, while that of € 
spermatocytes, first discovered in the synapsts persists through- 
out the divisions. 
his 
in of the bivalent chro- 
8. The spermatids become associated in groups to form 
colonies of nuclei lying in a common plasma. 
9. Within the latter arise bundles of fibres of great length, 
Whose connection with the nuclei could not be demonstrated, 
as well as single fibres of greater delicacy which are continu- 
ous with the nuclei. : - 
10. The mature sperm colony consists of a variable st a 
of filamentous nuclei contained, together with the er :. 
Cytoplasmic fibres, in a tenuous sheath which is flage!a 
its anterior extremity. 
urs very late. 
pue occ 
1 If such a connection is actual, it 15 slight and 
