The spermatogenesis of Peripatus (Peripatopsis) balfouri. 289 



periphery of the nucleus (Figs. 4, 5). In most cases it is seemingly 

 impossible to count the number of these chromatin loops. But in 

 one nucleus (Fig. 4) I could determine positively that not more than 

 three were present, and in others that the number of the loops was 

 certainly much less than the definitive number of chromosomes. Ac- 

 cordingly it would seem very probable that at an early stage a con- 

 tinuous chromatin spirem is formed. 



The nucleoli persist only through the dense spirem stage. 



The loose spirem stage (Figs. 6—13) is reached when the 

 chromatin loops have become shorter and thicker, as well as smoother 

 and denser. Concomitantly occurs a segmentation of the chromatin 

 into the separate chromosomes. In the arrangement of the chromatin 

 in the loose spirem stage a particular polarity of the nucleus can be 

 observed very clearly: viewed from one pole the chromatin loops 

 are seen terminally (Fig. 4), viewed from another surface of the 

 nucleus they are seen laterally (Figs. 5, 6, 8). Previously the 

 chromatin spirem had coursed through the nucleus more or less in 

 the form of a zig-zag, with sharp angles (Figs. 4, 5); these 

 angles are situated at what may be termed the pole side of the 

 nucleus, and it is at these angles that the segmentation separating 

 the thread into individual chromosomes takes place (Figs. 8, 9, 12). 

 ^Yhen the nuclear membrane disappears and the achromatic spindle 

 is forming, the chromosomes appear to take up more irregular 

 positions, thus it is difficult to determine, and indeed I could not 

 determine, whether an axis connecting the two poles of the nucleus 

 makes some definite angle with the axis of the achromatic spindle. 



At the time of segmentation of the spirem the loops usually 

 appear dense and homogeneous in structure (Figs. 7 — 13). But in 

 one cell (Fig, 6 a;, being one loop showing its details), each segment 

 of chromatin was clearly composed of serially disposed chromatin 

 discs alternating with faintly staining discs of linin. Whe shall find 

 that in the following anaphase the chromosomes break up into discs ; 

 and it would seem justifiable to conclude that in the prophase we 

 have a gradual approximation of discs. This view is generally held, 

 but so far as I recall no one has seen the discs as late as the loose 

 spirem stage. 



Now as to the relation of the chromatin to the linin, a connection 

 to which we shall recur frequently in our description. In the nucleus 

 of a spermatogonium we found single chromatin granules, or rows or 

 masses of them connected together by delicate linin threads (Figs. 1, 2). 



Zool. Jahrb. XIV. Abth. f. Morph. ]^(J 



