282 THE UNIVERSITY SCIENCE BULLETIN. 



1912b. Supernumerarv Chromosomes and Synapsis in Ceuthophiltis. 

 Biol. Bull., 22, pp. 219-231. 



Wilson, E. B. 1907. Note on the chromosome group of Metapodius and 

 Banasa. Biol. Bull., 12, pp. 303-313. 



1909. Studies on Chromosomes: V. The Chromosomes of Metapodius, 

 etc. Journ. ZooL, 6. pp. 143-215. 



1910. Studies on Chromosomes: VI. A New Type of Chromosome 

 Combination in Metapoditis. Journ. Exp. ZooL, 9, pp. 53-78. 



1911. The Sex Chromosomes. Archiv. fiir Mikr. Anat., Bd. 77, S. 

 249-271. 



EXPLANATION OF PLATES I, II, AND III. 



Drawings were made by aid of a camera lucida and are here repro- 

 duced at 2600 diameters. The pairs of autosomes are numbered, accord- 

 ing to size, from 1 to 6. The normal "accessory" chromosome is num- 

 bered 5x. The numeral 5 indicates that it ranks between the fourth and 

 fifth autosome in size. S designates the deficient supernumerary "acces- 

 sory" (?) chromosome. 



Figs. 1 to 5. Divisions in somatic cells each showing 14 choromosomes. 



Fig. 1. Fat body cell. No. 5's are foreshortened. 



Fig. 2. Cell from the follicular wall of the testis. Each large cromo- 

 some shows at the proximal end a peculiar somewhat knoblike portion, 

 which seems to be less deeply stained. The chromosomes are woolly. The 

 longitudinal split marked. 



Fig. 3. Cell from follicle wall. Follicle itself was full of spermatozoa. 

 Chromosome No. 5 is foreshortened. Each choromosome in figures 2 and 

 3 is split twice longitudinally. This may be seen by focusing on parts of 

 chromosomes running vertically. See cross-section of No. 4 at arrow 

 point. 



Fig. 4. One of the daughter cells, in a late anaphase or telophase of a 

 follicular cell. Distal ends of these chromosomes show the secondary 

 split. That which takes place at the division which follows the resting 

 stage into which this cell is about to pass. 



Fig. 5. Cross-sectional view of a daughter group of chromosomes in 

 the anaphase stage similar to figure 5. Chromosomes very long. The sec- 

 ondary split is quite visible. This cell will soon pass into the resting 

 stage. Cell taken from wall in region of the neck of the follicle. 



Fig. 6. Spermatogonium in metaphase stage of division. Fourteen 

 chromosomes. 



Fig. 7. Similar spermatogonium from another follicle. 



Figs. 8 to 21. Stages of first spermatocytes from early synapsis to 

 division. 



Fig. 8. "Sheaf stage," corresponding possibly to the "bouquet" stage of 

 other authors. The numbers of each of the six pairs of autosomes are 

 in parasynapsis at one end, probably distal, where six winding threads 

 may be counted. The normal accessory chromosome {5x) and its deficient 



