AND OF HYBRID PIGEONS. 
45 
valent in the ordinary dove-cot pigeons than in pure breeds of 
doves which have bred true for many generations. 
'fhat the irregularities of division in hybrids are due to 
degenerative processes going on in the tubules which give rise 
to deleterious chemical substances, is the first thought that pre¬ 
sents itself. This seems a very acceptable idea from what we 
know of the effects of drugs upon cell division, but it does not 
account for the fact that the primary spermatocytes are the 
cells attacked in the great majority of cases. 
Asymmetrical mitoses, through the researches of Hanse- 
mann"^, Lustig and Galeotti^ and others, are known to be of very 
general occurrence in carcinoma cells and other pathological 
tissues, and Galeotti^ and Schottlander^ among many others 
have determined that they may likewise be produced artificially 
in many tissues by treatment with dilute solutions of various 
drugs, such as quinine, chloral hydrate, cocaine, potassic iodide 
and antipyrin. 
A hybrid offspring is really a compound of two very differ¬ 
ent individual plasmas, hence conflicting tendencies must nec¬ 
essarily have been induced within its body. Most of the abnor¬ 
mality in division is in all probability but an attempt of each 
plasma to assert its individual activity. But why does this 
effort become apparent only in the primary spermatocytes ? 
The answer appears to be simply that there is no necessity for 
fusion of the components of the chromatin of cells except in the 
germ-cells at one stage of their maturation. Investigators have 
found that in maturation of germ-cells, a reduction of the or¬ 
dinary number of chromosomes to one-half occurs. Before 
this actual reduction there is ordinarily a so-called pseudo-re¬ 
duction in which the chromosomes fuse in pairs so that when the 
cell is ready for division, although only half of the regular num¬ 
ber of chromosomes appears, each is really double (bivalent) 
1. Hansemann, D: Karyokinese und Cellularpathologie.—Berl. Kin. 
Wochenschrift. No. 42 , 1891. 
2. Lustig and Galeotti: Cytologische Studien ueber pathologisehe men- 
schllche Gewebe.—Beitr. Path. Anat. XIV, 1893. 
3. Galeotti, G: Ueber experimentelle Erzengung von Unregelmassig- 
keiten des karyokinetischen Processes.—Beitr. z. patholog. Anat. u. z. Allg. 
Pathol.,XIV, 2, Jena, Fischer, 1893. 
4. Schottlander, J: Ueber Kern und Zelltheilungsvorgange in deno 
Endotheil der enzandeten Hornhaut.—Arch. f. mikr. Anat. XXX, 1888. 
