THE DIPLOID CHROMOSOME COMPLEXES OF THE PIG 197 



used at a temperature of four degrees Centigrade. The pieces 

 of tissue fixed must be very small and absolutely fresh (p. 158). 



Observations 



2. The number of spermatogonia! chromosomes is 40 (p. 162 

 figs. 1 to 20). 



3. The reduced or first spermatocyte number of chromosomes 

 is 20 (p. 164, figs. 21 and 22). 



4. The somatic chromosomes range in number from 40 to 

 58 — one cell with 74 chromatin bodies has been found (p. 165, 

 figs. 22 to 80). 



5. The 'extra' chromosomes divide as do the type chromo- 

 somes (p. 168, fig. 57). 



6. The variation in number is caused by the fragmentation of 

 certain chromosomes (p. 169). 



Analysis of the chromosome conditions 



7. The total length of the chromosomes ( X 20400) of the 

 spermatogonia varies from 118.6 cm. to 177.6 cm.; average, 

 136.9 cm. (p. 172). 



8. When the chromosomes are arranged side by side ac- 

 cording to length, they form a series which falls very gradually 

 from the long end to the short end of the series (p. 172). 



9. In such a series the chromosomes are found to lie in pairs 

 (p. 172). 



10. A fairly constant difference in length exists between the 

 pairs (p. 176). 



11. The total length of the chromosomes in the somatic 

 cells (x 20400) ranges from 117 cm. to 176.1 cm., showing these 

 cells to be within the spermatogonia! limits (p. 176). 



12. No tissue specificity of chromosome behavior has been 

 found (p. 165). 



13. The chromosome fragments are very nearly of even length 

 suggesting that the chromosomes lose a portion constantly rep- 

 resented by one or two chromosomes (p. 178). 



