THE SPERMATOGENESIS OF THE MYRIAPODS. 2OI 



are camera' lucida drawings of nuclei which show the origin 

 of the chromosomes as well as could be done even by the use 

 of diagrams. In Fig. 10 the karyosphere is very much reduced 

 in size and of an irregular shape ; from this three filamentous 

 projections extend, at the distal end of each of which is to be 

 seen a segment evidently only just detached. This is already 

 undergoing the process of tetrad formation. Fig. 1 2 represents 

 a considerably later stage in which the last chromosome is 

 leaving the karyosphere and the accessory chromosome is again 

 unmistakably to be seen. From these observations I believe no 

 other conclusion can be drawn than that stated above. 



To sum up briefly : At the time of the pseudo-germinal vesicle 

 stage, all the chromatin of the cell is aggregated in the karyo- 

 sphere which consists of a number of fine chromatin segments 

 closely massed about the accessory chromosome. In the suc- 

 ceeding prophase, the first change has to do with the loosening 

 of this mass of filaments. Later several ends become free and 

 by simply uncoiling, give rise to slender processes extend- 

 ing out into the nucleus. These become detached and new 

 threads are protruded until sixteen segments are present, which 

 together with the accessory chromosome make up seventeen, the 

 number of chromatin elements characteristic of the spermatocytes 

 of Scolopcndra. 



Several investigators mentioned before have traced in consider- 

 able detail the origin of chromosomes from nucleolus-like bodies. 

 Blochmann, '82 (Ncritina) says : " Das die Elemente der Kern- 

 blatte aus Theilstucken des Nucleolus entstehen, kann bei 

 unserem Objeke keinen Zweifel unterliegen, da ich alle Ueber- 

 gangszustande vom unversehrten Nucleolus bis zur angebildeten 

 Kernplatte beobachtet habe." In the germ cells of Mns a like 

 condition undoubtedly exists according to the investigations of 

 Hermann, '89; Roll, '93 ; and Sobotta, '95. Hermann reports 

 " chromatin nucleoli " as present in the cells at various stages of 

 spermatogenesis. Holl shows that in the germinal vesicle of the 

 mouse ovum there is a large nucleolus composed chiefly of 

 chromatin from the substance of which the chromosomes of the 

 first maturation mitosis are formed. Sobotta asserts that during 

 fertilization the chromatin of each pronucleus is in the form of 



