The spermatogenesis of Peripatus (Peripatopsis) balfouri. 367 



Fig. 247. Section through a testis with supernumerary (abnormal) 

 seminal vesicle: the testis proper {T) is cut longitudinally, the vesica 

 ( V) transversely (obj. C, oc. 2, tube length 100 mm). 



rig. 248. Nucleus of fibre cell of testis. 



Fig. 249. Transverse section of vas deferens (more distal portion), 

 yolk cell layer and spermatozoa not shown (obj. C, oc. 6, tube length 

 100 mm). 



Fig. 250. A segment of a transverse section of a mature testis (obj. C, 

 oc. 6, tube length 100 mm). 



Fig. 251. Longitudinal section of the region where the testis [T) 

 joins the seminal vesicle ( F) (obj. C, oc. 6, tube length 100 mm). 



Fig. 252. Longitudinal section of the region where the vas de- 

 ferens (^ Vas) joins the seminal vesicle ( V) (obj. C, oc. 6, tube length 

 100 mm). 



Plate 25. 



Figs. 253 — 256. Diagrams showing the evolution of the four main 

 types of chromosomes during the prophases of the 1st maturation 

 division. The arrows show the course of the evolution for each main 

 and each sub-type (the latter marked by Roman numerals) ; the lower- 

 most chromosome in each case is the definitive form. The central 

 {C.P.L'f and distal (D.P.L) linin threads shown in red, but the axial 

 liuin threads not represented. 



Figs. 257 — 261. Diagrams representing the relation of the chromatin 

 and linin from the stage of the spermatogonic monaster up to the be- 

 ginning of the rest stage of the 1st spermatocytes. The linin spirem 

 is shown in red, the secondary linin fibrils (Fig. 261) in black; in 

 Figs. 257 — 259 the axial linin threads of the chromosomes are not 

 shown, since in these stages they are hidden by the chromatin. For 

 the sake of clearness only 4 chromosomes (Chr) are shown. 



Fig. 257 shows the chromatin portions of the spirem segmenting 

 from one another, while the linin spirem still remains continuous. 



Fig. 258. Lateral view of a spermatogonic monaster, linin spirem 

 still intact. Mantle fibres shown in black instead of in red, since it 

 could not be determined whether in this mitosis they are derivatives 

 of the linin spirem. 



Fig. 259. Spermatogonic metakinesis, lateral view. The connective 

 fibres ( C. F) colored red since they are derivatives of the linin spirem. 

 The exact relation of the linin elements in this stage could not be 

 determined by actual observation, but are represented as deduced from 

 the facts observed in the preceding and following stages. A continuous 

 linin spirem present in each daughter plate of chromosomes, but the 

 portions of it (axial fibres) contained within the chromosomes not shown. 

 Probably the two daughter linin spirems are formed by a longitudinal 

 splitting of the single continuous mother linin spirem (of the preceding 

 figure). 



