84 GENETIC STUDIES ON A CAVY SPECIES CROSS. 



Bauer (1911) studied a cross between the self -fertile Antirrhinum 

 majus with the self-sterile A. molle and obtained dominance of self- 

 fertility. The F2 generation split up into self-fertile and self-sterile 

 forms, the majority being self-fertile, but the exact ratios were not 

 determined. Since A. molle is never self-fertile, Bauer interpreted the 

 phenomenon as physiological rather than mechanical. This case is a 

 peculiar kind of sterility, inasmuch as the gametes are not sterile except 

 in certain kinds of crosses. The inheritance of this peculiarity, never- 

 theless, follows Mendel's laws in its essentials. Bauer also reported 

 a cross between A. siculum and^. majus which gave sterile ovules and 

 fertile pollen. The pollen of these hybrids was capable of fertilizing 

 A. mo jus, segregation taking place subsequently. 



In plants, as in animals, the sterility following wide crosses is not of the 

 same sort always, for sometimes both sexes are sterile or partly sterile, 

 while in other cases one sex alone may be sterile or partly sterile. 



The literature on species crosses in mammals is meager, particularly 

 relatively to the inheritance of sterility. Compilations of species crosses 

 in animals by Ackermann (1897, 1898), Rorig (1903), and Przibram 

 (1910) give a fairly comprehensive conception of the amount of work 

 done. One is reminded of Bauer's (1911) statement: 



"Noch weniger als uber Bastarde zwischen Pflanzen-species, sind wir iiber 

 Artbastarde bei Tieren unterrichtet. Es sind zwar auch hier zahllose Art- 

 bastarde gelengentlich beobachtet oder auch kiinstlich erzeugt worden, aber 

 eine auch nur einigermassen geniigende Fj — Analyse est nie durchgefiihrt, ja 

 iiberhaupt nie versucht worden." 



Since so little is known of the inheritance of any characters in species 

 crosses in animals, it is not surprising that nothing is known of the 

 inheritance of sterility subsequent to such crosses. Sterility, to be sure, 

 often accompanies wide crosses in animals. In the Lepidoptera the 

 classical experiments of Standfuss (1895) have shown that such crosses 

 may give partial or complete sterility in either sex, gynandromorphs, 

 hermaphrodites, and even the complete suppression or elimination of 

 one sex. Recently Goldschmidt (1912) has attempted, on a Mendelian 

 basis, to explain gynandromorphism in the cross between Lymantria 

 dispar with L. japonica, upon the assumption that the factors for the 

 secondary sexual characters of the two parent species are of various 

 grades of potency. For our purposes it is not necessary to enumerate 

 all the species crosses resulting in sterility. These have been fully 

 recapitulated, summarized, and described by other investigators (Poll 

 1910, 1911; Przibram 1910). 



A few bovine crosses have yielded results somewhat similar to the 

 cavy crosses in this paper. Kiihn began a series of crosses, using the 

 genera Bibos, Bison, and Bos. The original papers were not accessible, 

 but a summary is given by Nathusius (1912). The yak, Bibos grun- 

 niens, has been crossed with the domestic cow. Bos taurus, and pro- 



