The Spermato genesis of Aplopus inayeri. 21 



wall; in figure 62 it begins to assume a bipartite form (a preparation for its 

 division in the telophase of the first maturation division). At this stage the 

 sparse cytoplasm of the primary spermatocyte frequently contains several 

 deeply-staining spherical bodies (fig. 63). These probably represent basi- 

 chromatin rejected during the last preceding mitosis or the succeeding synap- 

 sis stage, for such bodies are occasionally seen in process of transit from 

 the nucleus to the cytoplasm. 



Preparatory to the first maturation mitosis the nuclear reticulum passes 

 through the fine, coarse, and segmented spireme stages (figs. 62, 63, and 64). 

 These segments are at first delicate and stain intensely. Subsequently they 

 lose their staining capacity and assume a mossy or granular form. At this 

 stage a longitudinal split appears in the segments (figs. 65 and 66). This 

 is followed by a transverse split and typical tetrads are now formed, includ- 

 ing U and ring-shaped forms (figs. 67, 68, 69, 70, and 71). During these 

 changes among the ordinary chromosomes the accessory has retained its 

 compact form and intense staining capacity, though it appears in various 

 shapes (figs. 64, 66, 67, 68, 69, and 70). The splits in the tetrads close up 

 again and the chromosomes pass into the late prophase as compact, deep- 

 staining bodies, among which the accessory is only occasionally to be recog- 

 nized (fig. 73). In equatorial plates of the prophase spindle the accessory 

 chromosome can frequently be identified by its characteristic U -shape or 

 larger size (figs. 74, 75, 76, and 77). The number of chromosomes here 

 is 1 8. During metakinesis the bivalent chromosomes divide into two elon- 

 gate products of various sizes and shapes, most conspicuous among which 

 are long and short rods, cones, clubs, wide, shallow, U-shaped bodies, and 

 elements with the shape of short golf sticks (figs. 78, 79, 80, 81, 82, 83, 

 and 84). Usually a chromatin-connecting fiber remains until the early ana- 

 phase (fig. 83). The accessory meanwhile has passed undivided to one pole 

 and in advance of the ordinary chromosomes and generally retains a U -shape 

 (fig. 90). Occasionally, however, it becomes a double structure (figs. 81, 

 87, 88, 89, and 92), the result of a premature fission in anticipation of its 

 division in the secondary spermatocyte mitosis. Among the ordinary chro- 

 mosomes also some frequently appear double in the late anaphase and telo- 

 phase, thus also evidencing a premature division. 



During metakinesis a longitudinal split frequently appears in the ele- 

 ments of the dividing chromosomes (fig. 78). Thus the bivalent chromo- 

 some again assumes the tetrad condition of various forms (fig. 119). Upon 

 the question as to which of these splits represents the longitudinal split of 

 the early prophase and which the subsequently formed transverse split 

 hinges the decision as to whether the first maturation division is a reducing 

 or an equation division. In Scolopendra, Blachman (1903) finds a similar 

 sequence of events in regard to the chromosomes during the early prophase, 

 and on the basis of his own observations and the fact that " in all the inves- 



