SUTTON : SPERMATOGONIAL DIVISIONS IN BRACHYSTOLA MAGNA. 153 



spermatogonia and that of its more generally recognized fellows. Al- 

 though it shows a tendency to lag behind the other chromatic bodies, 

 the only radical difference between the two is the absence of the 

 loose spireme in the accessory, and this is paralleled, as shown above, 

 by the normal proce.ss of all the chromosomes of Pyrrhocorls, ac- 

 cording to the statement of Henking. The apparent radical difPer- 

 ence in the case of the vesicular stage is, in reality, only a matter of 

 degree, for it frequently hajopens that the ordinary chromosomes, in 

 going into the diffused condition, leave a very appreciable hollow in 

 their centers (fig. 30). Apparently there is, for some reason, a ne- 

 cessity that the chromatic granules of the accessory come into closer 

 relation with the cyptoplasm than those of its mates, and the result is 

 their deposition upon the vesicle itself — this vesiculation being really 

 a substitute for the loose spireme so conspicuously lacking. 



Now, if it be admitted that the body l,s a chromosome, inspection 

 quickly shows us that it maintains throughout the spermatogonial di- 

 visions, as well as in those that follow, an indubitable independence, 

 being enclosed, in all stages except those of actual division, in its own 

 individual membrane. Having, then, one of the chromosomes which 

 preserves its individuality in this way, and seeing the other chromo- 

 somes enclosed for a part of their development in similar individual 

 vesicles, which only become intercommunicating by absorption of a 

 part of their walls, have we not a right to suppose that at one time 

 they too enjoyed the same independence as their more exclusive mate'? 

 In other words, have we not a right to suppose that their phylogeny 

 is paralleled by their ontogeny? If this be granted, then we have at 

 least more ground for belief in the individuality of the chromosomes 

 than if we had never known of a time when they were of necessity 

 independent. 



III. T/ic S(iccnl<(t<'(l Xiicleiis. — In the reconstruction of the 

 nuclear membrane of the secondary spermatogonia of Biuic/n/sfohi, 

 we have to do with a condition hitherto undescribed, at least in this 

 sort of cells. This condition is the plurality of nuclear vesicles ex- 

 hibited at a certain stage of the prophase and retained in a modified 

 form until just before the following meta^jhase. 



The difference from the common type is not one of principle, but 

 rather of time relations. To make this clear, some explanation will 

 be necessary. It is generally admitted that the nuclear membrane of 

 all animal cells is formed between the already difPerentiated and sepa- 

 rate cytoplasm and karyoplasm as a result of certain activities of the 

 chromatin. Polar views of spermatogonia of Brncfiij^tola in meta- 

 phase often show a clearly defined hyaline area around some or all of 

 the chromosomes (fig. 2)^), and the same condition is sometimes to 



