The spermatogenesis of Peripatus (Peripatopsis) balfouri. 355 



and Batrachoseps (Kingsbury, 1899 ; Eisen, 1900), less clearly marked 

 in AmpUuma (McGregor 1899); it is least well marked in Sala- 

 mandra, though I judge it is the stage after the last spermatogonic 

 division characterized by Meves (1896) as "ein ausserordentlich dichtes 

 Chromatingerüst, das sich aus unregelmässig geformten Knoten und 

 düunern Bälkcheu zusammensetzt". Lee's (1897) figs. 8 and 10, and 

 Platner's (1886) figs. 8 and 23, are I think synapsis stages, and not 

 prophases of the spermatogonic mitosis of Helix as these authors 

 hold. Finally Born (1894) finds in the growth period of the germinal 

 vesicle of Triton that at certain stages the chromatin is arranged in 

 a body near the centre of the nucleus (his "Centralkörper") ; may not 

 this too represent a synapsis stage? 



From these references it follows that a synapsis stage would 

 seem to be a regular characteristic of the stage following the last 

 division of the spermatogonia and ovogonia. During it the reduction 

 in number of the chromosomes would seem in most cases to be 

 effected (but not in Ophryotrocha, according to Korschelt, 1895, nor 

 according to Calkins, 1895, in Lumhricus). 



In Peripatus and Pentatoma the synapsis is a portion of the 

 anaphase of the spermatogonic mitosis, and is followed by a complete 

 rest stage; this is also the case in Selachii (Moore, 1895), Ostracods 

 (Woltereck, 1898). McGregor (1899) and Meves (1896) look upon 

 it as the height of the rest stage, Henking (1890) and Paul>uer 

 (1899), as a prophase of the 1st maturation division; as also do 

 Hertwig (1890) and Brauer (1893) for Ascaris, who have described 

 it as preceded by a rest stage, but Sabaschnikoff (1898) makes no 

 mention of such a rest stage. Probably there is no such great vari- 

 ation in the time of occurrence of this stage as might be implied 

 by these different observations. From the last spermatogonic mitosis 

 to the first maturation division there is such a gradual succession 

 of nuclear changes, that no great stress need be laid upon the point 

 whether the synapsis is an anaphase of the last spermatogonic di- 

 vision, or a prophase of the first maturation division: it would all 

 depend upon how well marked the rest stage of the spermatocytes is. 

 Thus in Pentatoma I found a clearly marked rest stage, while Paulmier 

 in the closely related Anasa claims there is no rest stage in the 

 spermatocytes. The point of importance is that a particular synapsis 

 stage seems to be well marked in most objects, and that where it 

 does occur the reduction in number of the chromosomes takes place 



during it. 



23* 



