THE DIPLOID CHROMOSOME COMPLEXES OF THE PIG 185 



the bugs. Since the present paper deals with the diploid num- 

 ber alone, I will consider only that part of the reported mammal- 

 ian investigation. It is rather interesting to note the elaborate 

 descriptions of the resting and prophase conditions and the 

 brief consideration and few figures of the chromosomes them- 

 selves. The inference is rather obvious, and it is partly to 

 counteract the impression that sufficiently clear, and easily 

 studied chromosome complexes are scarce in mammalian material, 

 that I have presented the large number of figures at the close 

 of this paper. 



The investigation of the most importance to the present studx 

 is Wodsedalek's work on the pig ('13). He has reported 18 

 chromosomes in the spermatogonia and 20 in the ovary. He 

 also found two classes of embryos, one with 18 and the other with 

 20 chromosomes. He figured two X-chromosomes. The dis- 

 crepancy between Wodsedalek's count of 18 chromosomes and 

 my own of 40 chromosomes in the same type of tissue is rather 

 large, and I feel sure, has been due largely to the difference in 

 the methods of preparing the material. In a paper on ''The 

 fixation of mammalian chromosomes" ('17 b) I have described 

 the result of fixing mammalian tissue with various fluids, and 

 also the effect of fixing stale tissue (which, indeed, may not 

 have been removed from the body for more than 15 to 20 minutes). 

 Wodsedalek's figures are practically identical with those I have 

 found in either poorly fixed tissue or in tissue that was dead when 

 preserved. The chromosomes are clumped and undecipherable, 

 as is evident in the one spermatogonial and three embryonic 

 diploid cells figured in Wodsedalek's paper. A very interesting 

 condition seems generally to occur when chromosomes clump 

 together as the result of poor fixation. The number is reduced 

 to approximately one half through the fusion of chromosomes 

 lying along side of each other — probably mates. In the case 

 under discussion, Wodsedalek's count is two less than one half 

 of the count I have made. In this condition, such chromosomes 

 as can be distinguished at all, are at least double the width of 

 those found in properly fixed material. It is very evident that 

 such poorly preserved tissue should never be accepted as avail- 



